Sorry for the delayed reply.

First, if you haven't already, please do a normal shutdown and/or restart of your system. Restarting Windows can help by freeing up locked files, completing any deferred updates, and resolving temporary file permission issues.

Next, if Firefox still has bookmark problems, could you let us know what you get when you run the "Verify Integrity" diagnosis and repair function. That's here:

Open Firefox's Troubleshooting Information page using any of these methods:

• "3-bar" menu button > Help > More Troubleshooting Information
• (menu bar) Help > More Troubleshooting Information
• type or paste about:support in the address bar and press Enter

Near the bottom, there is a section titled Places Database -- that's the file which stores history and bookmarks. Click the button labeled Verify Integrity. There may be a 10-15 second delay before results appear.

If all is well, the report that appears below the button should start with:

> Task: checkIntegrity
+ The places.sqlite database is sane
+ The favicons.sqlite database is sane
> Task: invalidateCaches
+ The caches have been invalidated
> Task: checkCoherence
+ The database is coherent

Does yours say that, or something else? You can select and copy the report, and then paste it into a reply for review and comment.

Found a fix for my case (12/8/2025) see + below. History: Yesterday found Firefox updated to 145.0.2 (Windows 10), No bookmarks. "The bookmarks and history system will not be functional because one of Firefox's files is in use by another application. Some security software can cause this problem." Reboots, safe mode, stop Windows Shield, CCleanup, nothing helped. Tried other profiles, made a new profile, in all cases could NOT make/add new bookmarks! Fortunately I manually made a bookmark backup file last month when having a VERY SIMILAR PROBLEM back then, too. However Bookmark Manager would not let me Choose a file to restore from, no file list, nothing shown. Today again looking for a fix - found how to use about:support to verify places.sqlite database. Corrupt! For all profiles old and new. +Renamed it to places.sqlite-old to see if it would build a new and good version. Worked! Could now add bookmarks but really wanted previous bookmarks, theme, and extensions. +But, YAY, now Bookmark Manager would display the file list to Choose a restore from! It only listed the one backup file that I created last month, no automatic backup files listed anywhere. +But -YAY- Bookmarks, Theme, AND Extensions ALL restored! (Bookmark icons return when that site is visited.) Apparently places.sqlite serves ALL profiles. Folks --- make those bookmark backups!!! From now on I'll do both .json AND html. Wondering if corruption happened because we had a series of power failures rebooting the computer when Firefox was loaded -- but, then again, had a very similar bookmark problem last month too...

Edit: Now cannot make either type of backup file. I specify exact destination but does not work. Cannot find with global search either.

Edit: My theme and extensions did come back, but did not stick! So NOT a solution to get theme and extensions back, fortunately long ago made a text list, will work through it. Sigh. And go through settings. Sigh.