In Server Settings you should be using 'Authentication Method: Oauth2' for both incoming and outgoing. Google pop up is used by google to prove you are you and to ask whether to allow Thunderbird access to server. The password you enter will be the normal one you use to access webmail account, but as gmail uses Oauth the normal password is never going to be used by Thunderbird to get access to server. You may also get pop ups by google for address book and also calendar, so it would be helpful to know what that pop up is really refering to. Upload an image. If it really is for emails: * Access Settings > Privacy & Security * Click on 'Saved Passwords' You need to locate all the lines that have the 'username' for a problem address and remove them. But I recommend you do one account/username/email address at a time to avoid confusion as you mention more than one account. There should be at least one line for Oauth, but you might see an smtp or imap or mailbox line as well. Remove all of them. Exit Thunderbird and then restart. You should get a prompt for that particular username you removed from the Saved Passwords. Enter required data and set up to allow Thunderbird access. A new Oauth token should get stored for that username/email address. Check it has been stored and report back to let us know the Oauth token for that particular username was stored or not. Then remove the saved passwords for another username and repeat the action.