Issue: Adding a Gmail Account to Apple Mail - says Account Info is Incorrect

My Gmail account that I have used in Apple Mail for over one year has stopped working. Mid-February I received a notification that someone had tried to hack my Gmail acount, so I had to create a new password. Since then, my Gmail account in Apple Mail has gone offline and will not go back online, even when I enter the new, correct password.

I deleted the account and tried to re-add it, it says the account info is incorrect - what do I do?