kylefromca wrote:
Wally297 oh wise one!
How did you generate the app password? I'm assuming you mean Mac Mail???
Follow the directions on the first Google Support page to which BDAqua linked. Here's the same link, just with a more descriptive name.
Google – Gmail Help – Sign in with app passwords
Basically, Google tightened their security requirements. That is why connecting old versions of Mac Mail to Google – in the original way – broke.
There is a workaround. If your app or device cannot meet the new requirements, Google lets you generate an dedicated password (app password) for your "less secure" app or device to use to connect to Google's servers. Google generates the app password (see directions), and then, I believe, you use it instead of your normal Google account password when setting up new GMail accounts in older versions of Mac Mail.