One reason for the Add-ons page to have a blank extensions list would be some corruption in Firefox's database of extensions. You can force Firefox to regenerate the files by doing the following:

Open your current Firefox settings (AKA Firefox profile) folder using either

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

In the first table on the page, click the "Show Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then rename any of these files that you find:

• compatibility.ini to something like compatibility-old.ini
• extensions.ini to something like extensions-old.ini
• extensions.json to something like extensions-old.json
• extensions.sqlite to something like extensions-old.sqlite (might not exist depending on how long you've been using this settings folder)

When you start Firefox back up again, it should explore your profile folder, other folders, and the Windows registry to rebuild the list. It probably will ask you to approve some of the extensions. Once things settle down, could you check the Add-ons page again.

Do the extensions reappear?

Thank you for the reply. I followed the instructions and renamed those files (I did not have extensions.sqlite, but found the others.) However, when I restarted Firefox, Lastpass still does not appear, even though it's listed as "Always Activate" on the Plugins tab of the Add-ons page.

I should distinguish between the Plugins list and the Extensions list. In the left column of the Add-ons page, if you click Extensions, do you see LastPass there?

No, Lastpass isn't on the Extensions page, it shows up under Plugins.

The LastPass Plugin plugin show in the System Detail list, so at least Firefox finds the plugin. If the plugin isn't working then something else might be wrong.

See also:

• LastPass Password Manager: https://addons.mozilla.org/firefox/addon/lastpass-password-manager/

Okay, that either isn't right or is something new.

When I go to LastPass in Firefox and click FREE, it recommends something called the LastPass Universal Windows Installer, which says:

The Universal Windows installer installs browser extensions for Internet Explorer, Firefox, Chrome, Safari, and Opera.

https://lastpass.com/misc_download2.php

The thing you installed -- from the Chrome add-ons site? -- probably did not include all the parts for Firefox.

But at this point, if you have conflicting instructions, you may want to contact LastPass for advice on how to fix Firefox without creating problems in Chrome.

Ok, I've done some more research. Here's more info: The LastPass thing I see in the Plugins page is just a background thing that helps the system work. The real LastPass that should be appearing in the menu bar is actually an Extension, so my problem seems to be that I can no longer install extensions, and not just LastPass. Every extension I try goes through the motions, to the point where I get the screen "[name of ext] will be installed after you restart Firefox." Then I click Restart now, and after it restarts, the extension is not there, not on the menu bar, and not on the Extensions page. Any ideas? Thanks so much.

Try a new Profile. https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

Just a test, don't remove the current Profile.

Do your other extensions appear on the Add-ons page, or does Firefox think you do not have any extensions installed?

One reason for the Add-ons page to have a blank extensions list would be some corruption in Firefox's database of extensions. You can force Firefox to regenerate the files by doing the following:

Open your current Firefox settings (AKA Firefox profile) folder using either

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

In the first table on the page, click the "Show Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then rename any of these files that you find:

• compatibility.ini to something like compatibility-old.ini
• extensions.ini to something like extensions-old.ini
• extensions.json to something like extensions-old.json
• extensions.sqlite to something like extensions-old.sqlite (might not exist depending on how long you've been using this settings folder)

When you start Firefox back up again, it should explore your profile folder, other folders, and the Windows registry to rebuild the list. It probably will ask you to approve some of the extensions. Once things settle down, could you check the Add-ons page again.

Do the extensions reappear?

New profile did not help, renaming those files did not help. I have resorted to using Internet Explorer for now. I keep hoping Firefox will come out with another new version that will fix this, but not so far. Thanks to everyone who has taken a look at this strange issue.

Hi KamiCSPS, does removing the extension files allow the Add-ons page to work normally until the next time you exit and start Firefox, or the next time you shut down and restart Windows, after which it is blank again? Users with that pattern often have the BetterPrivacy extension, which had compatibility issues with Firefox 42 and was recently updated to resolve those issues: https://addons.mozilla.org/firefox/ad.../betterprivacy/.