Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• Click the menu button , click Help and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

the-edmeister, thank you. I tried it, but I still don't see my add-ons, even in a safe mode

It is possible that there is a problem with the file(s) that store the extensions registry.

Delete the extensions.* files (e.g. extensions.json, extensions.sqlite, extensions.ini) and compatibility.ini in the Firefox profile folder to reset the extensions registry.

• https://support.mozilla.org/kb/Profiles

New files will be created when required.

See "Corrupt extension files":

• http://kb.mozillazine.org/Unable_to_install_themes_or_extensions
• https://support.mozilla.org/kb/Unable+to+install+add-ons

If you see disabled or not compatible extensions in "Firefox menu button/Tools > Add-ons > Extensions" then click the Tools button at the left end of the Search bar to check if there is a compatibility update available.

If this hasn't helped then also delete the addons.json file.

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox

I'll try. Will my add-ons be disabled when I delete these files?

No, this doesn't delete the extensions. This merely reset the database that stores installed extensions. Firefox may ask for permission to install globally installed extensions. If there are other problems then click the cogwheel on the about:addons page and do a check for updates.

cor-el, thank you so much! It works now.

cor-el said

No, this doesn't delete the extensions. This merely reset the database that stores installed extensions. Firefox may ask for permission to install globally installed extensions. If there are other problems then click the cogwheel on the about:addons page and do a check for updates.

I had the same problem. I did those yesterday and it worked. Today it went back to the way it was not showing up the extensions.

Rose1 said

cor-el said

No, this doesn't delete the extensions. This merely reset the database that stores installed extensions. Firefox may ask for permission to install globally installed extensions. If there are other problems then click the cogwheel on the about:addons page and do a check for updates.

I had the same problem. I did those yesterday and it worked. Today it went back to the way it was not showing up the extensions.