What was the last version of Firefox that worked with LastPass? Or is this your first time installing the extension?

Normally extensions will appear on the following tab. If an extension is disabled, it will be in a grayed out section at the bottom. Can you find it down there?

orange Firefox button (or Tools menu) > Add-ons > Extensions category

If you have trouble installing any new extension, one of your settings files might have become corrupted. Rather than post lots of steps that might be irrelevant, please let us know if you think that would be worth pursuing.

If you actually are running Firefox 21 now, there is another possibility. The LastPass extension appears to offer the possibility to install either in your personal settings folder (AKA profile folder) or in the "application folder". In Firefox 21, the "application folder" has moved. You might try reinstalling the add-on in your profile folder if you didn't do that the first time.

LastPass appeared as an extension. I changed the LastPass settings so that I have to log into LastPass with my master password when I launch FireFox. It seems that if my LastPass vault remains open in one of the tabs, it performs properly. This is different than how it behaves in Internet Explorer.

I will close this problem as solved and thank you very much for your help.

P.S. I had removed and then re-installed the LastPass add-in but, although I'm using FireFox 21, it didn't give me an option as to where it would be installed.

Hi HuntingtonFred, I haven't used LastPass. If it seems unnecessarily inconvenient in Firefox compared with other browsers, there might be another setting that isn't obvious, to make it easier. You might try LastPass support or forums for suggestions.

What I've done is make LastPass my home site so when I launch FireFox, I log into LastPass and leave the LastPass vault page in an open tab. Then when I log into another site which requires a login and password which I've previously set up in LastPass, LastPass logs me into that site automatically. LastPass is a free password manager that works well in IE. Any time LastPass detects a login page, it enables you to set up the password and ID in its database and fills in the login info at future login prompts. My solution for FireFox is a bit clunky but when I need to use a second browser, it works.