In the end the only solution I found was to go in to my Google account and turn off secure apps or more precisely swich to allow unsecure apps. As soon as I did this I can access my gmail account again OK but it does beg the question why does Google NOW consider the Thunderbird application to be insecure.
Gmail. Includes private messaging features. Wonderful spam protection. Gives you 15 GB of space …
How to Setup Windows Live Mail To Access Gmail Using IMAP Jul 08, 2016 Add an email account to Outlook - Office Support Gmail, Yahoo, iCloud, Outlook.com, and AOL accounts all use two-factor authentication to help verify that you’re the person trying to access your email account. To add your email account to Outlook, you’ll need an app password, also known as an application password. This is a different password than your regular email account password.
How can I stop someone else from using my Gmail account
My Account To update your password today, log into My Account, select your email profile and click the edit option next to password. Find All Gmail Accounts Linked To Your Phone Number