This morning I discovered that for one of my GMail email accounts it kept popping up a Google screen wanting me to re-authenticate. It had already filled in my email address but whenever I clicked the button to go to the next screen where it should have asked for the password, it kept going back to the screen that asked for my email address, and I could never get past that. I finally just deleted the account in Thunderbird out of frustration, thinking maybe if I re-created it from scratch it would solve the issue but when attempting to re-create the account I still had the same issue - I can't get past that screen where it ask for my email address; it never gets to where it asks for the password. I can log in to that GMail account with no problem using Firefox but for some reason it doesn't work in Thunderbird, but only for that one Gmail account. And I have been using this account in Thunderbird for months now so don't get what happened this morning that would cause this issue.