Oceniono na 5 z 5 możliwych gwiazdek
I had the same problem with login to Google as https://addons.thunderbird.net/sk/thunderbird/addon/open-google-calendar/reviews/1163926/
The solution was quite simple. Instead of clicking the existing account on "Choose an account" page, I clicked "Add account" link. This allowed me to enter my google credentials again and everything worked fine.