Firefox Community Forum

Whenever i send a Tab from any Device to a Linux Desktop, the Linux Desktop is almost guaranteed to freeze. It doesn’t matter if that Linux Desktop is my "Dingus" PC with 2GB RAM and Wayland, or my "Workstation" PC with 16GB RAM and X11. On both Desktops, Firefox runs smoothly until it gets sent a Tab from another Device, then the whole Linux Desktop freezes. The Desktop doesn’t slow if i open the Tab on the Desktop in the “Tabs from other Devices” Sidebar instead.

Only my Linux Desktops freeze when they get sent a Tab from another Device. Android doesn’t slow when my Phone gets sent a Tab from another Device.

Today Firefox has suddenly started using ~20% of my CPU capacity, causing my cooling fan to run high most of the time. Since I had been running Firefox v.149.latest, I tried updating to v.150.0, but that made no difference.

It's not Firefox by itself (only Task Manager open) but whenever I open another tab with almost any website (including this one) that CPU usage spikes. What gives?!

Details: Running under Windows 10 Pro (yes, I have installed the ESU package, good until thi8s fall) on a Lenovo P1 Gen 2. Currently running Firefox inside a Sandboxie Pro v1.17.4 sandbox.

Please Help! -- jclarkw

Hey everyone!

I just noticed that post FF's 150 update, I can no longer drag and drop folders into my DSM window. This has been a non issue for over 6 years and all of a sudden, poof. I did find that you can still to this on Safari, but long term, Mozilla and Synology need to address this. There's already a post on the Synology fourms about it and I've emailed their Support Team to see what they have to day. Posting this here in case anyone has found a workaround in the Config settings pane.

Thanks! --Brian

Firefox 150.0.1 Ubuntu 22.04

Problem: When downloading a file from a web page, the list of files and folders in the Download Panel are sorted such that file names and folder names are intermingled, rather than the "standard" folders first, then files.

Discussion: This problem has been happening for a bit now (probably 2 - 3 months or more). Unfortunately, I don't recall exactly which version of Firefox this originally showed up in. At some point recently, the default sort for the Download Panel changed, so that instead of listing folders at the top of the list of download targets, then listing files, now all items are interspersed. For example, previously selecting to download a file from a web page would give the Download Panel contents as:

AFolder BFolder CFolder AFile.txt BFile.pdf CFile.jpg

Now, the list presents as:

AFile.txt AFolder BFile.pdf BFolder CFile.jpb CFolder

I would like to go back to the previous sorting behavior, but I cannot find a way to do this. I have searched the Mozilla help articles without turning up relevant information, and I have searched the internet for web sites that might list relevant information, but either the information I am seeking is not out there (unlikely) or I am not coming up with search terms that locate the information (much more likely).

I am not even 100% sure that this is a Firefox problem (it is within the bounds of possibility that it is an OS problem), but none of my other regularly used programs show the symptom, so it would seem odd to me for it to be something other than a Firefox problem.

I would appreciate any pointers (web pages, help articles, or even just "change this in about:config) on how to resolve this.

Je ne peux plus accéder à Facebook sur l'ordinateur. Attente éternelle de la prise en compte des mes codes. Alors que j'y accède normalement sur mon téléphone portable et sur ma tablette. Je suis protégé par Bitdefender. Quid ? Merci :-)

ie every time I closed it it would reopen- 14 times when I am trying to read my emails yesterday and 6 today. but I thought it was my internet security causing the problem. I kept getting notification that a certain site was attempting to use my system,. The worst thing was it kept flashing on my screen and wouldn't go away, There was no clue who öwned it, my security or Mozilla's. It was finally resolved by contacting my computer guy, but we never identified the source. the site that was being blocked started with pssst.........com, or something similar but it was driving me mad trying to get it off the screen. If this happens again, how do I get rid or stop the continual notifications? Of course I have nothing to show you as I have since deleted it, sorry. as I was just relieved to see it gone.

Thank you Angela Johnson

Moderator note: This question has been edited to correct the formatting.

Over the past few weeks, my typing is continually being interrupted. It did this a few years back, but this is getting very annoying and I am soon to switch browsers if not fixed. BTW on any machine using Firefox, this is happening

Hi,

I shared a lot of important tabs to my laptop (using the firefox built-in share/send to other device button), upon starting it, they seemed to arrive just fine and opened on my laptop, however I accidentally clicked to "history"->"restore last session", which made this firefox window go away and all my sent tabs seem lost.

Is there any way to get them back? Any type of log?

I tried the following already: - Looking through History (they do not appear there at all) - Looking at recently closed tabs (there aren't any listed) - checking synced tabs window (did not contain the ones I sent from my phone to my laptop) - checked session recovery files ( none of my synced tabs seem to have gotten stored into that session recovery file)

So is there any other log or place I can look at? I refuse to believe that this is not saved anywhere? Or on mozilla servers at least? Can support help me?

Thanks for any ideas!

EDIT: I found this, may is something similar: https://connect.mozilla.org/t5/ideas/send-tabs-log/idi-p/15640

About a week ago I had printed 2 copies from my Firefox browser. Next time I only needed 1 and changed it. Since then it stays at 2 and no matter what I do it won't go back to one.

How do I fix this?

I've tried to access each of 3 new TP-Link EAP 770 access points' web interface using current version of Firefox on a Mac and a Windows 11 laptop and I believe there's some security setting blocking the access. Usually, I would receive the warning with an "Advanced" button to allow you to continue to the web interface, but now I only receive a "Looks like there's a Problem with the Site" with a "Try Again" button. I had an older Windows 10 laptop with an older version of Firefox that actually allowed me to access one of the access points, but after the laptop had been online for a few minutes (and updated the Firefox version) my access started to fail again. Any help is appreciated.

Thanks, JB

When I press F12 to use the developer tools and try to change the width of the panes by click and drag the divider there now seems to be a limit to the panes width that was not there before. I'm not sure with what version I stated to notice this. I use to be able to drag the right hand panel fairly far over to the left and could take up about 75-80% of the width of the developers window. Now I'm guessing that I'm able to drag the right panel to a max width of 35-40% for some reason. I have not changed anything in the about:config page. I'm not sure why I can't drag the right panel to cover the 75-80% of the window that I had been able to do.

Is there a setting in the developer tools or on the about:config page that sets the max width that the right hand panel can be dragged to the left?

Hi,

two days ago, video embeds on Twitter stopped working in Firefox. Please help me troubleshoot the issue, so that I can either fix it myself, or present enough evidence to file a proper bug report.

Affected version: FF 140 ESR. I had some 140.7 installed when the error first happened, but have upgraded to firefox-esr_140.10.1esr-1_amd64 since. Didn't fix the problem. *Not* a snap package, regular .deb!

Affected OS: Ubuntu 26.04 LTS, not a fresh install but upgraded from 24.04 instead (which itself was upgraded from 22.04).

Symptoms: Videos on X (and Facebook) no longer play, the preview image is there for a split second, then an error appears. Video on for example Youtube is fine, though. Local players like VLC also do work as expected. Video on X worked under 26.04 before this happened.

The issue likely started when removing surplus packages and metapackages from the upgrade. According to synaptics, this is the complete list of packages removed: augeas-lenses bomber bovo clevis clevis-luks db-util db5.3-util dolphin-dev gir1.2-freedesktop-dev gir1.2-glib-2.0-dev girepository-tools gostsum granatier guestfish guestfs-tools guestmount icu-devtools jose kapman katomic kblackbox kblocks kbounce kbreakout kdegames kdegames-mahjongg-data-kf6 kdiamond kfourinline kgeography kgeography-data kgoldrunner kigo killbots kiriki kjumpingcube klickety klines kmahjongg knavalbattle knetwalk knights kolf kollision konquest kreversi kshisen ksirk ksnakeduel kspaceduel ksquares ktuberling ktuberling-data kubrick kubuntu-web-shortcuts ldmtool libaom-dev libarchive-tools libaugeas0 libblkid-dev libconfig11 libdbus-1-dev libdlt3 libffi-dev libfmt-dev libfontconfig1-dev libfribidi-dev libgd-perl libgio-2.0-dev libgio-2.0-dev-bin libglib2.0-dev libglib2.0-dev-bin libgraphite2-dev libguestfs-perl libguestfs-tools libguestfs0t64 libharfbuzz-cairo0 libharfbuzz-dev libhivex0 libicu-dev libjose0 libjson-glib-dev libjxr-tools libjxr0t64 libkdegames6private6 libkmahjongg6 libldm-1.0-0t64 libmosquitto1 libmount-dev libosinfo-1.0-0 libosinfo-l10n libpcre2-dev libpixman-1-dev libpolkit-gobject-1-dev libpsl-dev libpwquality-tools libpython3-dev libpython3.14-dev libselinux-dev libsepol-dev libspdlog-dev libsqlite3-dev libssh-dev libstd-rust-dev libstring-shellquote-perl libsys-virt-perl libsysprof-capture-4-dev libsystemd-dev libtirpc-dev libusb-0.1-4 libusb-1.0-0-dev libusb-1.0-doc libusb-dev libvirt-common libvirt0 libwebsockets19t64 libwhoopsie-preferences0 libwhoopsie0 libwin-hivex-perl libx265-dev libxdo-dev libxdo3 libxft-dev libxkbcommon-dev libxrender-dev libyara10 lskat lskat-data mosquitto mosquitto-clients native-architecture osinfo-db palapeli palapeli-data picmi qml6-module-org-kde-games-core skladnik supermin whoopsie whoopsie-preferences I don't think they are related (libx265 and libaom are only the -dev packages), but this is the only system-wide change on that day that I can remember. I of course tried re-installing these, but this also doesn't fix the problem.

On my journey of fixing this myself, I also asked the all-hallucinating knowledge randomizer frontend of OpenAI, which made me check a couple generic spots on my system and in FF itself.

ffmpeg -codecs | grep -E "h264|hevc|vp9|av1" ffmpeg version 8.0.1-3ubuntu2 Copyright (c) 2000-2025 the FFmpeg developers

 built with gcc 15 (Ubuntu 15.2.0-13ubuntu3)
 configuration: --prefix=/usr --extra-version=3ubuntu2 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --disable-pocketsphinx --disable-libcaca --disable-libmfx --disable-omx --enable-gnutls --enable-libaom --enable-libass --enable-libbs2b --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libglslang --enable-libgme --enable-libgsm --enable-libharfbuzz --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-openal --enable-opencl --enable-opengl --disable-sndio --enable-libvpl --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-ladspa --enable-libbluray --enable-libdvdnav --enable-libdvdread --enable-libjack --enable-libjxl --enable-libpulse --enable-librabbitmq --enable-librist --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libx264 --enable-libzmq --enable-libzvbi --enable-lv2 --enable-sdl2 --enable-libplacebo --enable-librav1e --enable-librsvg --enable-shared
 WARNING: library configuration mismatch
 avcodec     configuration: --prefix=/usr --extra-version=3ubuntu2 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --disable-pocketsphinx --disable-libcaca --disable-libmfx --disable-omx --enable-gnutls --enable-libaom --enable-libass --enable-libbs2b --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libglslang --enable-libgme --enable-libgsm --enable-libharfbuzz --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-openal --enable-opencl --enable-opengl --disable-sndio --enable-libvpl --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-ladspa --enable-libbluray --enable-libdvdnav --enable-libdvdread --enable-libjack --enable-libjxl --enable-libpulse --enable-librabbitmq --enable-librist --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libx264 --enable-libzmq --enable-libzvbi --enable-lv2 --enable-sdl2 --enable-libplacebo --enable-librav1e --enable-librsvg --enable-shared --enable-version3 --disable-doc --disable-programs --disable-static --enable-libaribb24 --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libtesseract --enable-libvo_amrwbenc --enable-libsmbclient
 libavutil      60.  8.100 / 60.  8.100
 libavcodec     62. 11.100 / 62. 11.100
 libavformat    62.  3.100 / 62.  3.100
 libavdevice    62.  1.100 / 62.  1.100
 libavfilter    11.  4.100 / 11.  4.100
 libswscale      9.  1.100 /  9.  1.100
 libswresample   6.  1.100 /  6.  1.100
DEV.L. av1                  Alliance for Open Media AV1 (decoders: libdav1d libaom-av1 av1 av1_cuvid av1_qsv) (encoders: libaom-av1 librav1e libsvtav1 av1_nvenc av1_qsv av1_vaapi av1_vulkan)
DEV.LS h264                 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (decoders: h264 h264_v4l2m2m h264_qsv h264_cuvid) (encoders: libx264 libx264rgb h264_nvenc h264_qsv h264_v4l2m2m h264_vaapi h264_vulkan)
DEV.L. hevc                 H.265 / HEVC (High Efficiency Video Coding) (decoders: hevc hevc_qsv hevc_v4l2m2m hevc_cuvid) (encoders: libx265 hevc_nvenc hevc_qsv hevc_v4l2m2m hevc_vaapi hevc_vulkan)
DEV.L. vp9                  Google VP9 (decoders: vp9 vp9_v4l2m2m libvpx-vp9 vp9_cuvid vp9_qsv) (encoders: libvpx-vp9 vp9_vaapi vp9_qsv)
DEAIL. wmav1                Windows Media Audio 1

-> ffmpeg is installed, version 8, av1 and hevc support seems present. The sparse advice from google results (similar thing in a Gentoo forum I think) on installating ffmpeg4.4 is no longer viable. --- apt list --installed | grep libavcodec

libavcodec-dev/resolute,now 7:8.0.1-3ubuntu2 amd64 [installed] libavcodec-extra62/resolute,now 7:8.0.1-3ubuntu2 amd64 [installed,automatic] libavcodec-extra/resolute,now 7:8.0.1-3ubuntu2 amd64 [installed]

(libavcodec62 non-extra was installed before, didn't change anything) --- apt list --installed | grep libaom*

libao-common/resolute,resolute,now 1.2.2+20180113-1.2ubuntu2 all [installed,automatic] libao4/resolute,now 1.2.2+20180113-1.2ubuntu2 amd64 [installed,automatic] libaom3/resolute,now 3.13.1-2 amd64 [installed,automatic] --- FF about:support in the codec section says this: Codec Support Information Codec Name Software Decoding Hardware Decoding H264 Unsupported Supported VP9 Supported Supported VP8 Supported Supported AV1 Supported Unsupported HEVC Unsupported Supported AAC Unsupported Unsupported MP3 Supported Unsupported Opus Supported Unsupported Vorbis Supported Unsupported FLAC Supported Unsupported Wave Supported Unsupported --- vainfo Trying display: wayland libva info: VA-API version 1.23.0 libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/iHD_drv_video.so libva info: Found init function __vaDriverInit_1_22 libva info: va_openDriver() returns 0 vainfo: VA-API version: 1.23 (libva 2.22.0) vainfo: Driver version: Intel iHD driver for Intel(R) Gen Graphics - 26.1.2 () vainfo: Supported profile and entrypoints

     VAProfileMPEG2Simple            : VAEntrypointVLD
     VAProfileMPEG2Main              : VAEntrypointVLD
     VAProfileH264Main               : VAEntrypointVLD
     VAProfileH264Main               : VAEntrypointEncSliceLP
     VAProfileH264High               : VAEntrypointVLD
     VAProfileH264High               : VAEntrypointEncSliceLP
     VAProfileJPEGBaseline           : VAEntrypointVLD
     VAProfileJPEGBaseline           : VAEntrypointEncPicture
     VAProfileH264ConstrainedBaseline: VAEntrypointVLD
     VAProfileH264ConstrainedBaseline: VAEntrypointEncSliceLP
     VAProfileVP8Version0_3          : VAEntrypointVLD
     VAProfileHEVCMain               : VAEntrypointVLD
     VAProfileHEVCMain10             : VAEntrypointVLD
     VAProfileVP9Profile0            : VAEntrypointVLD
     VAProfileVP9Profile2            : VAEntrypointVLD

--- running with MOZ_DISABLE_HW_DECODE=1 firefox -> no change --- A fresh profile shows the same issues, so this should not be config-related in terms of Firefox --- Safe mode on my standard profile also doesn't change anything --- running with MOZ_LOG="PlatformDecoderModule:5" firefox -> also no change, but now on every try to play a video, these three lines are spammed: [Child 2326924: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type video/avc [Child 2326924: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type video/av1 [Child 2326924: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type video/hevc

On other websites, the occasional [Child 2330726: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type audio/mp4a-latm or [Child 2331802: Main Thread]: D/PlatformDecoderModule Sandbox Utility Generic decoder rejects requested type video/vp8

is added.

Some time close to starting FF, this block is presented: [Utility 2331783: Main Thread]: D/PlatformDecoderModule PDMInitializer, Init PDMs in Utility process [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFMPEG: version: 0x200, macro: 62, micro: 101, isFFMpeg: yes [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFVPX: Link result: Success [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder rejects requested type 'video/avc' [Utility 2331783: Main Thread]: D/PlatformDecoderModule Agnostic decoder rejects requested type 'video/avc' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/vp9' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/vp9' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/vp8' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/vp8' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/av1' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'video/av1' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder rejects requested type 'video/hevc' [Utility 2331783: Main Thread]: D/PlatformDecoderModule Agnostic decoder rejects requested type 'video/hevc' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder rejects requested type 'audio/mp4a-latm' [Utility 2331783: Main Thread]: D/PlatformDecoderModule Agnostic decoder rejects requested type 'audio/mp4a-latm' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/mpeg' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/mpeg' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/opus' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/opus' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/vorbis' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/vorbis' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/flac' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/flac' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/x-wav' [Utility 2331783: Main Thread]: D/PlatformDecoderModule FFmpeg decoder supports requested type 'audio/x-wav' [Parent 2331581: Main Thread]: D/PlatformDecoderModule Broadcast support from 'Utility Generic', support=H264 NONE VP9 SW VP8 SW AV1 SW HEVC NONE AAC NONE MP3 SW Opus SW Vorbis SW FLAC SW Wave SW

Back in FF 140.7, I also got these lines, but they're no longer present in 140.10 or flags have changed, I don't know: [Child 2238921, MediaDecoderStateMachine #1] WARNING: Decoder=7329b02ba900 state=DECODING_METADATA Decode metadata failed, shutting down decoder: file ./dom/media/MediaDecoderStateMachine.cpp:371 [Child 2238921, MediaDecoderStateMachine #1] WARNING: Decoder=7329b02ba900 Decode error: NS_ERROR_DOM_MEDIA_METADATA_ERR (0x806e0006): file ./dom/media/MediaDecoderStateMachineBase.cpp:168

--- The troubleshooting info below this text box says this somewhere:

"name": "AV1_HW_DECODE",
         "description": "AV1 hardware decoding",
         "status": "blocklisted",
         "log": [
           {
             "type": "default",
             "status": "available"
           },
           {
             "type": "env",
             "status": "blocklisted",
             "failureId": "FEATURE_FAILURE_VIDEO_DECODING_MISSING",
             "message": "#BLOCKLIST_FEATURE_FAILURE_VIDEO_DECODING_MISSING"
           }

Open to suggestions on where to dig deeper next...thank you!

bold text On brand new DELL Alien-ware laptop with Windows 11 Firefox sometimes takes 30 seconds to open, Also once it is closed it cannot immediately open again. Error message shows Firefox is already opened and asks me to close it.

In the task manager under Apps running I see Firefox(12) when only the home page is open. Are those 12 hidden tabs or 12 parallel applications?

Have I made some errors in the Setup?

I am subscribed to a newsletter and ever so often firefox doesn't allow communication with the comments. This has happened several times and I have always corrected the problem in firefox, I have forgotten how I corrected the problem, For me this is an ongoing problem any suggestions?

I have my credit card info correctly saved in the FF settings on my PC desktop, but it doesn't work correctly on some online forms.

When it fails to work I click on the truncated information for the saved credit card I wish to use, but it fills in later numbers in the sequence incorrectly with the wrong digits and too few numbers to even be a legitimate credit card number

I have double checked in the settings, "privacy and security", and the credit card numbers are entered correctly there and enabled.

The form I have most recently had issues with were for a local "big day of giving" site, and it is powered by something called "mighty cause."

I can't include a screenshot of the issue itself occurring or my settings, for obvious reasons.

My PC is windows 11 home edition, and the version of Firefox is 150.0.1 (I think).

When I click Bookmarks > Manage Bookmarks I'm taken to Other Bookmarks where I never store anything. I'd delete it if I could but it doesn't appear to be an option, so instead I'd like to taken directly to Bookmarks Menu. I came across this post from just over 4 years ago which sounded like it's exactly what I want, but it doesn't work. Are there any changes anyone can suggest that would allow it to work in 2026?

https://support.mozilla.org/en-US/questions/1373437

You can use the autoconfig.cfg file in the Firefox installation folder to initialize (set/lock) preferences and run privileged JavaScript code. In this case code to open the Library with the Bookmarks Menu folder selected. You can modify the showPlaces variable to open any of the four possible root folders (in this case [1]).

To use Autoconfig, place two files into the Firefox installation directory.

   on Windows and Linux, they go into the same directory where Firefox is installed
   on macOS, they go into the Contents/Resources directory of the Firefox.app 

The autoconfig.js file that specifies to use autoconfig.cfg is placed into the "defaults\pref" directory where the channel-prefs.js file is located.

The autoconfig.cfg file is placed at the top level of the Firefox directory.

   autoconfig.cfg and autoconfig.js need to start with a comment line (//)
   autoconfig.js needs to use Unix line endings (LF instead of CR/LF) 

See also:

   https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig 

Content of autoconfig.js

//
pref("general.config.filename", "autoconfig.cfg");
pref("general.config.obscure_value", 0);
pref("general.config.sandbox_enabled", false); // disable sandbox to allow privileged JavaScript

Content of autoconfig.cfg

// first line in autoconfig.cfg is a comment line try {

let {classes:Cc, interfaces:Ci, manager:Cm, utils:Cu} = Components;
var Services = globalThis.Services || ChromeUtils.import("resource://gre/modules/Services.jsm").Services;

function ConfigJS() { Services.obs.addObserver(this, 'chrome-document-global-created', false); }
ConfigJS.prototype = {
 observe: function (aSubject) { aSubject.addEventListener('DOMContentLoaded', this, {once: true}); },
 handleEvent: function (aEvent) {
  let document = aEvent.originalTarget;
  let window = document.defaultView;
  let location = window.location;
  if (/^(chrome:(?!\/\/(global\/content\/commonDialog|browser\/content\/webext-panels)\.x?html)|about:(?!blank))/i.test(location.href)) {
   if (window._gBrowser) {
     let showPlaces = ["AllBookmarks","BookmarksMenu","BookmarksToolbar","UnfiledBookmarks"][1];
     elm = document.getElementById("Browser:ShowAllBookmarks");
     if (elm) {
      elm.setAttribute("oncommand", "PlacesCommandHook.showPlacesOrganizer('"+showPlaces+"')");
     }
   }
  }
 }
};
if (!Services.appinfo.inSafeMode) { new ConfigJS(); }

} catch(e) {Cu.reportError(e);}

On all other browsers the drop down menus still show after first use, except in Firefox - where after first use they disappear and you have to go back to Home to re-show them.

I have tried the suggestions give for configuring the site iin Elementor/Wordpress but none have solved the problem and I can only assume the answer lies in Firefox settings.

TIA

When I click on option/link for "Print using the system dialog box", the print preview no longer works. Instead I see message "This app doesn't support print preview" in preview pane.