Everyone that is experiencing this issue, please submit a ticket to their support, the more of us that submit something, the more likely they will be to address the issue.https://support.logmeininc.com/lastpass
I did, and now they are asking some questions.
Here are the questions they asked, you might try to head off the questions by answering in the initial contact:
Could you please provide us with more details about the issue? (I gave them the versions of FF, Windows (including build #), and the Extension)
Do you receive any error messages?
When did this issue start to occur? (Obviously I stated this started with the new version of the extension)
Please try disabling and re-enabling the 2FA and see if the issue still persists. (NOTE: I told them I refused to do this step, this is a BS troubleshooting step, it should work regardless of 2FA or not).
Is the issue solely for Firefox? Please see if the issue occurs on other browsers.
Is/was Firefox ever set as a trusted device?
As a last resort, see if reinstalling the extension can solve the issue. (this was the very first thing I tried)
Please send us a screenshot or a short video of the issue so we can further assess it. (NOTE: I provided 4 screen shots of each step from clicking on the browser add-on button, through to the spinning circle, screen shots or a video will show them what is happening).