Firefox Community Forum

Hello,

I have had an issue for a few months now where certain websites fail to load. This is most easily reproduced on https://addons.mozilla.org, where I am shown the error "An unexpected error occurred" on most pages, preventing me from installing addons.

This issue does not occur in a Private Window, in Troubleshooting mode or in Chrome or Brave, but persists in fresh installs of Firefox. In troubleshooting this issue, I have removed all program files, registry data, and app data pertaining to Mozilla / Firefox. In fresh installs, I can sometimes install an add-on or two before this error starts occuring. I have not imported any previous data.

I was previously installing from Chocolatey, but in my last clean install, I downloaded from the official website.

I am on Windows 10 and Firefox 157. I use Proton VPN (Paid) and have tried changing servers several times to no avail. Again, this only happens in Firefox in a standard window, Private Mode and Troubleshooting Mode are fine.

Screenshot 1 shows the issue from my most recent reinstall. I was able to install 1 add-on (SponsorBlock) before it started showing up. Removing the add-on doesn't fix the issue. Trying to access addons.mozilla.org via a search engine results in the tab icon loading for a second and no change happening on screen (Screenshot 2).

I experience similar issues on other websites, like trying to log into Bandcamp.com (logging in gives the error "There was a network error. Please try again."), but most sites work.

Loading https://addons.mozilla.org/en-US/firefox/ gives the following results in the Network Console:

Uncaught (in promise) TypeError: can't access property "pressed", target is null

   onChangePermissions chrome://mozapps/content/extensions/components/addon-card.mjs:893

addon-card.mjs:893:7 Reporting Header: invalid JSON value received. collect Reporting Header: invalid JSON value received. collect Reporting Header: invalid JSON value received. collect Reporting Header: invalid JSON value received. collect Reporting Header: invalid JSON value received. collect Reporting Header: invalid JSON value received. collect

I regularly consult this web-site https://eservices.dls.moi.gov.cy/#/national/geoportalmapviewer It is a government land registry website. A lot of it still works (the least useful parts) I need to use the Interactive Maps but now instead of a nice map of Cyprus I got a message saying there was a problem with the web-site. I accordingly switched off enhanced in the shield and now get "The specified URL cannot be found. " Aaaargh! I've raised a query with them but I'd just as soon learn from anyone who could help. Thanks

Hi,

I’m having an issue while using a web proxy service in Firefox. I’m trying to access Croxyproxy Croxyproxy, but I’m not sure whether the problem is related to Firefox settings, cookies, JavaScript, or Tracking Protection.

Has anyone experienced similar issues when using Croxyproxy with Firefox? Are there any Firefox settings I should check to make sure the website works correctly?

Thanks for your help.

Your VPN has not been working in Russia for 5 days now. Just to write this, I have to wait about a minute on every page. Why does your browser work so slowly in the support section? The same site opens much faster in Chrome.

I'm using Windows 10 on a PC. Norton Security app is preventing web browsing by Firefox. The message I get is: "We prevented your connection to ful.hartonly.com because it is a dangerous webpage. Threat category: URL:Blacklist" I can still web browse using Google Chrome without any problem. What is ful.hartonly.com and how do I clear it?

when visiting websites using my vpn firefox blocks my entry. I have to disconnect my vpn to allow entry to sites. ive tries numerous fixes and nothing works its frustrating.

April 21, 2026 Tuesday

Thank you for your being here as a volunteer to answer this type of question:

IS eset.com security software compatible with Firefox Mozilla ?

Thank you,

Oliver Jeffrey

east@west.net 24/7 LA California

I have been unable to access any secure sites since I installed Norton 360 Antivirus. Whenever I try to access a secure site I receive the reply: Secure Connection Failed Error: PR_END_OF_FILE_ERROR I have tried all of the repairs listed on the internet but none have corrected the fault. I have also tried disabling Norton but also without success I have also tried uninstalling and re-installing Firefox but without success Can you suggest any other methods to correct this fault

I would like to know what are the best Antivirus Protection to use with Firefox. Previous information is from 2011 and I would like to get more current information. Thank you

why am i being asked to sign in to age verification sites when i have mozilla paid VPN installed and have enabled japan as the start point rather than UK  ? - Thanks