Immediately after updating to macOS Sequoia 15.7.8, Google accounts stopped authenticating in Apple Mail. Internet Accounts shows Mail enabled, but the accounts do not appear in Connection Doctor or remain inactive in Mail. Removing and re-adding the accounts does not resolve it. Other users are reporting the same behavior after 15.7.8.
Issues with Sequoia 15.7.8, Gmail and Apple Mail
We appreciate your interest in participating in the forums! These forums are for questions about developing software and accessories for Apple platforms. Your question seems related to a consumer feature and is better suited for the Apple Support Communities
https://discussions.apple.com/welcome
Hope this helps
Albert WWDR