Could I ask a few questions: (1) When did the problem start? (2) Do you recall any software changes around that time (either system updates or app updates or add-in installations)? (3) What have you tried so far? For example, Firefox Refresh, virus scan, etc. The user in the following thread did a very drastic cleanup which probably flushed all the data that couldn't be recovered from Sync: https://support.mozilla.org/questions/1386798 It sounds like you want to try some less destructive steps first. (1) Virus scans. Our support article lists tools that are free or have a free trial and other Firefox users have found helpful. [[Troubleshoot Firefox issues caused by malware]] (2) New Profile Test. Steps below the line. (3) Clean reinstall. Steps below the line. ---- One method to suss out an issue with settings or add-ons is: '''New Profile Test''' This takes about 3 minutes, plus the time to test problem site(s)/feature(s). Inside Firefox, type or paste '''about:profiles''' in the address bar and press Enter/Return to load it. Take a quick glance at the page and make a mental note of which Profile has this notation: '''This is the profile in use and it cannot be deleted.''' That is your current default profile. Click the "Create a New Profile" button, then click Next. Assign a name like Test2023, ignore the option to relocate the profile folder, and click the Finish button. Firefox will switch your default profile to the new one, so click the '''Set as Default Profile''' button for your regular one to avoid an unwanted surprise at your next startup. Scroll down to Test2023 and click its '''Launch profile in new browser''' button. Firefox should open a new window that looks like a brand new, uncustomized installation. (Your existing Firefox window(s) should not be affected.) Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system to get a clean test. ''Does the new profile window have the unexpected yellow border?'' When you are done with the experiment, you can close the extra window without affecting your regular Firefox profile. (Test2023 will remain available for future testing.) '''Clean Reinstall''' ''This assumes you run Firefox downloaded from Mozilla rather than from the Windows store. This might cause data loss with the Windows store version.'' This takes about 5 minutes. This doesn't clear your settings, but it removes folders that might contain Policy and AutoConfig files that can override standard operations. It is not necessary to uninstall Firefox, but you can if you like, saying No to any request about removing personal data. (A) [Optional] Back up your Firefox data. See: [[Back up and restore information in Firefox profiles]]. (B) Download a fresh installer for Firefox to a convenient location: https://www.mozilla.org/firefox/all/#product-desktop-release (C) Exit out of Firefox (if applicable). ''If you use '''Microsoft Office''', please change your default browser to Edge temporarily before the next step.'' (D) Using Windows File Explorer/My Computer (hold down the Windows key and press E to launch it), right-click > rename the program folder as follows (you might have one or both): Open C:\Program Files and look for Mozilla Firefox If you see it, right-click Mozilla Firefox, click Rename, and rename it to OldFirefox Open C:\Program Files (x86) and look for Mozilla Firefox If you see it, right-click Mozilla Firefox, click Rename, and rename it to OldFirefox (E) Run the installer you downloaded in step (B). It should automatically connect to your existing settings. Any improvement at your next startup?