Solved! Lastpass MFA 30 day wait for reauthentication for Firefox not working


Background

I have Lastpass Premium extension running in Firefox and Chrome in a Windows 10 laptop. I just added MFA using Google Authenticator and expected my device to stay trusted for 30 days before having to re-authenticate. This worked for Chrome, but failed for Firefox. Firefox kept needing reauthentication. I opened a ticket with Lastpass

The problem I reported to Lastpass

I just today set up Google Authenticator. I ticked the box for trusting my device for 30 days. I did this for both Firefox and Chrome. But in Firefox, it keeps reprompting me to authenticate every time I close and reopen my Firefox browser.  

Solved! The solution given to me by Lastpass 

If you are using Firefox 57+, you will need to have the browser accept Third-party cookies to allow LastPass to remember email and remain logged in. To find this setting:
  1. Click on the hamburger icon (three horizontal lines) on the top right corner of the browser
  2. Go to Options
  3. Go to Privacy & Security
  4. Under "History", enable "Use custom settings for history"
  5. Enable "Accept cookies from websites" and set "Accept third-party cookies" to Always
Note: If you have "Clear history when Firefox closes" enabled, please go to the settings and disable "Cookies".