Hello. Could you let me know what exact error message Outlook shows when it tries to connect to your Gmail account?
You can also try this:
- Close Outlook
- Go to https://myaccount.google.com/security
- Open “Third-party apps with access”
- Look for “Microsoft apps & services” and remove it
- Open Outlook again and add your Gmail account back
A user on the Google forums described this same fix here: https://support.google.com/mail/thread/336041814/can-t-sync-office-21-outlook-with-gmail