When I attempt to sign into my work email (a Gmail account, authenticated via Okta) account, the browser popup window uses an accounts.google.com/signin/oauth/legacy URL, and on clicking 'Allow' attempts to redirect to http://localhost, which of course is not going to be picked up by Thunderbird. So, after clicking, the button is disabled, the window hangs, and I'm never authenticated. Oddly, this flow has worked before for this account, and I only have to reauthenticate because of a required password change.