Using an antivirus other than defender? A firewall other that windows firewall? A VPN?

For all of the above stop them and try again after a reboot and with them still stopped.

Thanks for the email. I turned off McAfee antivirus and firewall, restarted and tried again to set up the gmail and yahoo mail accounts, but to no avail. I didn't expect to have such a hurdle to set it up but so far that's the case and still not working. Any other suggestions? Horatio

Check that cookies are accepted in TB Settings/Privacy & Security, as that's necessary for gmail and Yahoo OAuth2 authentication. Still not working, test in TB safe/troubleshoot mode (hold Shift on TB start). Still not working, run Windows in safe mode.

I've tried everything suggested so far except that I cannot login in safe mode.The fingerprint is not an option, there is a comment about the PIN sign in not being available and then a link to download a third party PIN setup app which doesn't load, of course. This is really something :))

Firewall - whether you use the default Windows Firewall or the Anti-Virus which controls the Firewall.

You need to have Thunderbird program set up as allowed program otherwise it gets blocked.

I'm using Norton Anti-Virus and it controls the Firewall. I know you are not using Norton but the image below shows what needs to be set as allowed. The Thunderbird exe file and also the Thunderbird update exe file.

If you have a VPN enabled then switch it off. Servers do not like it as they think you might be a hacker.

If you have any program using the 'localhost' such as Apache Xampp then switch it off until the Oauth token has been set up. If you have a website then you may be using programs that use the localhost.

In Thunderbird

• Settings > Privacy & Security
• Web Content
• Select 'Accept cookies from sites
• Accept third party cookies 'Always'
• Click on 'Exceptions'
• Add the following and set up as allow. https://accounts.google.com
• click on 'Save Changes'

If you have accessed Google or yahoo webmail account and set up to use 2 step verification then you will need to create an 'app specific password'. This also means you will need to alter the Authentication Method when setting up mail account. Alternative is to switch off 2 step verification.

• Menu app icon > New Account > Email
• Enter name
• Enter email address
• Enter Password - please note this is the normal password you use to access webmail.. BUT if you have set up an app specific password then you must use the app specific password.
• Select checkbox to remember password
• click on 'Continue'

Thunderbird will attempt to locate correct server settings. By default it sets up for IMAP and sets Authentication Method as Oauth.

IF you have set up to use 2 step verification and are now using an 'app specific password', you will need to click on 'Configure Manually' Then alter the 'Authentication Method' to use 'Normal Password' instead of 'Oauth2' for both incoming and smtp outgoing. User name = full email address. click on 'Retest' and 'Done' to create account.

IF you have switched off 2 step verification or never set up, then you are using Authentication Method Oauth which means you entered the normal password and not the app specific password. This means you will then get a google/yahoo pop up window asking for normal password and then you select to allow Thunderbird access to server.