Hello, Go to your profile folder: *[https://support.mozilla.org/en-US/kb/profiles-tb#w_how-to-find-your-profile How to find your profile] Close Thunderbird, unhide the hidden files and folder: *[http://kb.mozillazine.org/Show_hidden_files_and_folders] Delete or rename the''' key.db '''and''' singons.sqlite'''

I have the same issue, via two-factor authentication. Should I revoke this for Thunderbird? Please read below and weigh in. I enabled two-factor authentication for GMail, and managed it for Thunderbird, too. A little different than described on GMail support. Mozilla discourages it ([http://kb.mozillazine.org/Gmail http://kb.mozillazine.org/Gmail] http://kb.mozillazine.org/Gmail, about 4/5 of the way down). As part of the GMail process, since my Thunderbird is hosted by GMail, GMail generates a 16-letter App password. My old password no longer worked, and I enetered the App password to get into Thunderbird. Now I'm stuck with a 16-letter string as my Thunderbird password?? Several forums reference the Password Manager, in which I have nothing saved. The forums cite this article: [http://kb.mozillazine.org/Setting_and_changing_email_passwords http://kb.mozillazine.org/Setting_and_changing_email_passwords] http://kb.mozillazine.org/Setting_and_changing_email_passwords. Alternatively, there's Diego Victor's above reply. Before doing this, I would want to know what these two files do, and why it's OK to delete or rename them. Finally, I could try revoking the App password for Thunderbird. I have no idea what effect this would have.