It seems a [https://support.mozilla.org/en-US/questions/1157498 bug from 2017] (that has been fixed in an earlier release) resurfaced: I changed my Gmail password in the Google Accounts web interface. Opening my Gmail account on Thunderbird then causes an OAuth authentication window to popup, as expected. It asks for an email address, which I input. Then I click on the 'next' button, but instead of going to the password entry field, it brings me back to the starting point where it asks me for an email address. This loop goes on without end, preventing me from successfully authenticating with Gmail from Thunderbird. These symptoms match [https://support.mozilla.org/en-US/questions/1157498 the earlier bug report] precisely (and [https://askubuntu.com/questions/910327/thunderbird-stuck-at-google-sign-in AskUbuntu question here], [https://askubuntu.com/questions/910614/why-cant-i-progress-beyond-entering-my-username-when-configuring-thunderbird-to/910630#910630 here], and [https://bugzilla.mozilla.org/show_bug.cgi?id=1359383 Bugzilla report here]). I know there is the workaround to downgrade to regular SMTP authentication by toggling the 'Allow access to less secure apps' option in Google Accounts and then changing the authentication mechanism in Thunderbird, but OAuth is preferable of course. System setup: - macOS 10.11.6 - Thunderbird 68.7.0 (release channel)