Does https://support.mozilla.org/en-US/kb/cannot-receive-messages help?

Thanks Wayne, but I've tried those options to no avail, Plus I'm on version 91.10.0. If you any other ideas I'd love to hear them.

https://support.microsoft.com/en-us/windows/start-your-pc-in-safe-mode-in-windows-92c27cff-db89-8644-1ce4-b3e5e56fe234 then start Thunderbird while holding shift key to start in troubleshoot mode.

Better results?

Sorry, it didn't work. I can't believe I'm the only one having this problem??

It is possible the Firewall thinks the updated Thundrebird is a different program and so it is blocking it. So you need to check this first.

Exit Thunderbird. Access Firewall. It might be the Windows OS default one or if you are using an Anti-Virus then it might be controlling the Firewall. Is Thunderbird set up as an allowed program? If no then add it. If yes, then block it /remove (depends upon what options you get) and select OK/Save. Access Firewall again and set up Thunderbird as an allowed program.

What server are you using ? Is it gmail ? IF yes, then it is possible gmail are blocking access.

Thunderbird has made alterations so now both POP and IMAP accounts can use OAuth2 for gmail. Do the following

• Select 'Menu app icon' > 'Preferences' > 'Privacy & Security '

Under 'Web Content'

• Select 'Accept cookies from sites'

It may also be a good idea to make exception:

• Click on 'Exceptions..' button
• Enter: https://accounts.google.com
• Set to 'Allow'
• click on 'Save Changes'

Some people have needed to remove the old stored passwords, so I suggest you do this whilst you are in the 'Privacy & Security'.

• Scroll to 'Passwords' section
• Click on 'Saved Passwords'
• Click on 'Show Passwords'
• Make a note of the password
• Select the mailbox://(if pop) or imap:// (if imap) and smtp:// lines and click on 'Remove'.
• Click on Close

Now make changes to Account Settings:

• Right click on gmail pop/imap account name in Folder Pane and select 'Settings'

This opens the Account Settings in new tab The pop/imap account name should be selected Look bottom right for Outgoing Server (SMTP)

• Click on 'Edit Server _SMTP' button
• Set Authentication Method : OAuth2
• Click on OK

Now set the incoming authentication:

• select 'Server Settings' for gmail account
• Set Authentication Method : OAuth2

Exit Thunderbird and wait a few moments for background processes to complete

Before you restart Thunderbird - double check that the password is correct. You can only do that by trying to logon to the gmail webmail account using a browser.

Start Thunderbird

Gmail will prompt you to enter gmail email address and normal password you use to access webmail account. Follow instructions. It will ask this to allow Thunderbird to access server.

An Oauth token will get stored in Thunderbird - same place as passwords and from then onwards Thunderbird will use it to access server.