Extension installations don't complete. They get stuck at <extension name> "will be installed after you restart Firefox." Restarting Firefox doesn't change this
I was always able to install extensions without any problems up until a couple days ago. Since then, the extension installation process gets stuck at the point where they show up in the list of extensions (about:addons) with the message <extension name> "will be installed after you restart Firefox." Restarting Firefox has no effect on this -- after the restart, the extension still says "will be installed after you restart Firefox." I've tried restarting Firefox several times, and I've tried installing other extensions, and the same thing happens with every extension I try to install.
I know I'm running an outdated version of Firefox, but please ignore that. I have a good reason for that.
Chosen solution
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.
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/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 possible addons.json and addons.sqlite files.
You can check for problems with preferences.
Delete a possible user.js file and numbered prefs-##.js files and rename (or delete) 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 the current Firefox release.
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Chosen Solution
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.
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/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 possible addons.json and addons.sqlite files.
You can check for problems with preferences.
Delete a possible user.js file and numbered prefs-##.js files and rename (or delete) 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 the current Firefox release.
Thanks very much! I had to do all the things you listed, but it did solve the problem.