I've been using Thunderbird for more than 15 years. Last year, it suddenly stopped downloading e-mails with a message about sending password information to the server, but then does nothing. I tried various privacy and server settings but nothing worked. However, Thunderbird works fine on another laptop. Now I've migrated to a new PC, was able to copy the profile over to the new PC but the problem persists. At the same time, a different profile on the new PC works fine. I read something online about a popstate file that might be causing the server to not respond, but even deleting that did nothing. Another thought I've had is to move all the old email to the new profile, but everything I've read online talks about moving the entire profile which I have done but the problem remains the same. Old profile has all the old e-mails but doesn't get any new ones, and the new profile downloads the new incoming e-mails but of course doesn't have the old e-mails.