It is possible that there is a problem with files in the profile folder that store the extensions registry.

Delete the extensions.* files (e.g. extensions.json, extensions.ini, extensions.sqlite) 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 ""3-bar" menu button or Tools > Add-ons > Extensions" then check if there is a compatibility update available.

• click the cogwheel button (left of Search bar)

If this didn't help then delete add-ons.json and possibly prefs.js in case there is a problem with preferences.

Delete possible user.js and numbered prefs-##.js files and rename/remove the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in current Firefox releases.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

There is software like Advanced SystemCare with its Surfing Protection feature that can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

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

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

if i have to be a programmer to understand the answer, then I probably don't need to ask the question. Maybe firefox is just for computer geeks.

That's why we are here, to answer questions and give support when needed.

FredMcD said

That's why we are here, to answer questions and give support when needed.

Really? Yet you add no additional help to the previous incomprehensible answer to this question. no one who can understand it needs it. I need it, but can't understand it.

Type about:support in the address bar and press enter.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

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.

After, restart Firefox.

See "Corrupt extension files":

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

You will have to approve the updating one last time.

This issue was previously pursued (by myself and others) in the thread at https://support.mozilla.org/en-US/questions/1091072, Alas, that thread has been archived.

After being upgraded to FF 44.0 back in December 2015, I followed advice similar to that given by cor-el above. It didn't work. (See previous thread for the details, including screen shots.)

The problem continues. It just happened after my latest upgrade to FF 46.0. Since the earlier thread has been archived, I'll carry on here.

I just followed cor-el's instructions posted at 3:00p today. (Thanks, cor-el!) When I restarted Firefox, all those "Install Add-On" tabs are still there. Perhaps cor-el's last sentence, "You will have to approve the updating one last time.", means that the problem has been fixed even though the tabs are still appearing this time. If so, that would mean I need to wait till the next FF upgrade to confirm this. Right, cor-el?

You could try to make a backup copy of the extensions.json and extensions.ini files and possibly prefs.js to see if they haven't changed after a reboot. Also verify that Firefox updates them properly after you close the browser. I don't know if the problem is with the extensions.json file or with prefs like extensions.*addons.

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

• "3-bar" menu button > Exit (Power button)
• Windows: File > Exit
• Mac: Firefox > Quit Firefox
• Linux: File > Quit

If you use "Clear history when Firefox closes" then try to disable this feature.

Thanks, cor-el. It seems to me that, since I have now manually re-enabled all my add-ins after the upgrade to FF 46.0, there is no point in my trying any of these additional things until the next FF upgrade. Right?

If it works for now then there is no need to do further Troubleshooting. Hopefully it won't happen again on the next start. You can try to close Firefox yourself via "File > Exit" or the button in the "3-bar" Firefox menu button drop-down list instead of clicking a button in the update window (Help > About) or in a pop-up alert if an update needs to be applied.