Yes, I just wasted a full two hours running in circles trying to follow the recommendations of the "experts" I know NOTHING of emails (and plan to stay ignorant)

The answer is in a reddit post: https://www.reddit.com/r/Thunderbird/comments/v7ziud/how_i_fixed_oauth_problems_in_a_tb_profile_with_2/ "The gmail popups won't let me enter passwords... it just refreshes over and over with the email account box. Yes the accounts are still valid and working."

Go to Thunderbird -> Preferences -> Privacy and Security In the Web Content section:

ACCEPT ALL COOKIES - it is as yet unclear whether should be only all third party ect. and how long to keep them

This IMMEDIATELY worked and all of my mail since June 6th downloaded

Please run through the following and check you have all the following set up. I'll post a couple of comments, so check them in order I post.

Thunderbird has made alterations so now both POP and IMAP accounts can use OAuth2 for gmail. Have you done all of 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'

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 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.

Additional:

Note: Gmail may advise to switch on 2 step verification. This is not necessary because you are using OAuth.

Some people have needed to remove the old stored passwords.

• Menu app icon > Preferences > Privacy and Security
• Under 'Passwords' section
• Click on 'Saved Passwords'
• Select the mailbox://(if pop), imap:// (if imap) and smtp:// lines and click on 'Remove'.

Restart Thunderbird.

Some people run a localhost server eg: Apache This must be switched off and then retry. You should be able to use the google prompt. You can switch Apache back on afterwards. Note: In some Linux systems Apache may have been auto installed, so even if you think it is not installed please check.

If you find you keep being asked for password and in :

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

You discover passwords and cookies are not being saved then do this:

• Menu app icon > Help > More Troubleshooting Information
• Under 'Application Basics' - Profile Folder - click on 'Open Folder'

This opens a new window showing the contents of your current in use profile name folder.

• Exit Thunderbird now - this is important.

Look for the following files and delete them.

• cert8.db - obselete file
• key3.db - obselete file
• pkcs11.txt (some people report this file missing)
• secmod.db - obselete file
• session.json
• xulstore.json

NOTE: Do NOT delete:

• key4.db
• cert9.db
• logins.json

Start Thunderbird New pkcs11.txt, session.json, xulstore.json files will get created.

Retry entering password etc at prompt.

Please note: If you run software that cleans up files like CCleaner or WiseCleaner or even some Anti-Virus products can do this - then please make your Thunderbird profile folder exempt. You do not want any of your eg: session. password, cookies etc being removed by anything.

Check : Are you running a VPN because gmail may not like it? Switch it off.

I use Norton 360 Anti-Virus and discovered an auto update had installed and switched on a VPN without my knowledge. It took some tracking down Switched it off and all started ok again.