Hi, Everything has been working for several years, up until November 4th (about a month ago). Since November 4th, every time I navigate to any of my Gmail folders in Thunderbird, I get the Thunderbird browser popup for authenticating to Google, I log in, select "Allow", and then get an error from the Thunderbird app (not the Thunderbird browser), "Authentication failure while connecting to server imap.gmail.com". (Screenshot attached). I've followed everything in this article: https://support.mozilla.org/en-US/kb/automatic-conversion-google-mail-accounts-oauth20 Namely: In Thunderbird: confirmed cookies enabled, confirmed no entries for cookies or saved passwords, confirmed Javascript enabled, confirmed IMAP OAuth selected In Gmail: confirmed IMAP is enabled, confirmed Thunderbird has been granted account access I've also cleared Thunderbird's disk cache, and Thunderbird's web history ("Everything"). Any ideas? Thanks! Dan