I Haven't had any replies as yet but have found the problem after comparing the setup on another PC. The fault lies not with Firefox but with Kaspersky Free AV. I don't know what caused it but assume it was an overnite Kaspersky database update.

I exited Kaspersky then uninstalled the reinstalled Firefox the tried an the Lastpass logged in and opened. I restarted the PC along with Kaspersky and I could login and open the vault. So this was solved but I couldn't then open the Account Options. Opening Kaspersky I then went to Security Settings/Network Settings and turned off the Mozilla Firefox and Thunderbird certificate store which was set to use the Windows certificate store (recommended) and the Account Options now works. The other PC uses Kaspersky Security Cloud Free and there is no problem there so I'm assuming there was/is an issue with Kasperky Free AV using the certificate store. Doesn't have an issue with MS Edge.

This may help others if they have the same issue with Firefox / Lastpass and Kaspersky.

Same symptom: have the Lastpass extension set up as my homepage in Firefox (current version 99.0.1; 64-bit). Have had this set up for years. It has happened before, but has become routine the last week or so. When opening Firefox, I log in to Lastpass, but the vault doesn't open, and clicking the Lastpass icon in the browser toolbar present nothing--no options (such as to open vault). I do NOT use Kaspersky (have Comodo Security suite installed for antivirus). I don't see any settings in Comodo to select which cert store it uses.

Any suggestions would be appreciated.

Hi jeffh. I suggest you file your own question.

Why would I file a separate question, when the issue appears to be identical? Firefox extension for Lastpass isn't working properly. I uninstalled, reinstalled yesterday, worked fine until just a few minutes ago, when it did the same thing: the red icon with 3 dots appears in the toolbar, but clicking it does not display any of the options (open vault, etc) that are expected. Instead, it's just blank. So, 2nd day in a row, had to uninstall/reinstall to get the functionality.

If the extensions are not the purview of Firefox/Mozilla support, let me know, so I won't be wasting my time in here.

Hi jeffh,

Search for this article on the Kaspersky web site and try the suggestion for importing certificates -

How to add the Kaspersky root certificate to the Mozilla Firefox or Thunderbird certificate storage.htm

Even if there is no specific setting in Comodo to change Network settings, this may be applicable. Although it deals with Kaspersky AV specifically, there may be an entry in your Windows Certificates authority for Comodo and if so you could try the additional steps for importing the certificate into Firefox.