I'm offering a complete set of things to check out. '''Check Password:''' Logon to your webmail account via a browser -if you can do this and see emails then you know the password is good. * Confirm password works. Whilst in webmail account.... Confirm - do you see new incoming emails that have not been downloaded to your Thunderbird imap account? It's important to know the gmail account is still receiving mail. '''Checks on computer:''' '''Firewall:''' Access Firewall - it might be the default on computer or controlled by an Anti-Virus prgram you installed. Set up Thunderbird program as 'allowed' so nothing gets blocked. Do not switch off Firewall as that will not help. * Confirm Thunderbird is set up as allowed program. '''VPN:''' Check computer for a VPN. Some Anti-Virus products now offer a VPN and I have come across some peopl who did not realise one had been enabled. So do not assume anything. Switch off VPN (or create split tunnelling and set it up for Thunderbird to use). Gmail does not like VPN as it atempts to hide your IP address, so gmail decides you might be hacker so it auto blocks access. * Confirm VPN is switched off '''Localhost:''' Do you have anything using the localhost? People who manage websites may typically use eg: Apache Xampp. You need to switch of any program using the localhost whilst setting up gmail OR resetting the oauth password token. You can enable it again afterwards. I had to switch off Apache Xampp. * Confirm nothing is using localhost. '''Checks In Thunderbird''' * Settings > Privacy & Security * Web Content * Select 'Accept cookies from sites' * Click on 'Exceptions' button * Enter this : https://accounts.google.com * Click on 'Allow * Click on 'Save Changes' Whilst in that area - scroll to Passwords section * click on 'Saved Passwords' * If you see any mention of the account you are trying to set up (username = gmail email address) - You may see lines that begins with: * * imap://imap.gmail.com( * * smtp://smtp.gmail.com( * * oauth://accounts.google.com( * select any relevant lines and click on 'Remove' - I'm advising you remove everything in order to reset the Oauth token. * Click on Close '''IF you want to completely reinstall the imap account:''' * Access 'Account Setting' * select gmail account and click on 'Delete' located top right. I would switch off the following as it's still experimental. * Settings > General * Account Hub * uncheck this checkbox: 'Create accounts in the new Account Hub' Then create the mail account * Menu app > New Account > Email * Enter name * Enter gmail email address * Enter password * Select checkbox to remember password. * Click on 'Continue' Thunderbird by default will look for the IMAP server settings. Whether recreating the gmail imap account afresh '''OR''' if you decide to keep it - these are the server settings for imap account. So check you have the correct settings. They should be: '''IMAP''' * Server name: imap.gmail.com * Port: 993 * Connection Security: SSL/TLS * Authentication Method: OAuth2 * Username = full gmail email address * Password is the same one you use to access webmail '''Outgoing SMTP:''' * Server name: smtp.gmail.com * Port: 465 * Connection Security: SSL/TLS * Authentication Method: OAuth2 * Username = full gmail email address * Password is the same one you use to access webmail If recreating a new imap account - Assuming all is ok click on 'Done' If creating new gmail imap account OR you have kept original,but removed stored passwords as advised..... You should then get the gmail pop up browser type window. It will ask you to confirm you really are you and the then ask if you want to allow Thunderbird access to server. Then an OAuth token gets created and stored in the same place as all other passwords.