No notification sound from Mail app on iOS 15.0.1

Hi, my new iPhone 13Pro just updated to iOS 15.0.1 and now I won't hear any sound notification or vibration when a new email arrives.

I use Gmail in the Mail App and all notifications are enabled, I don't use Focus or Do Not Disturb. I receive the emails correctly (not a fetch issue), and the notification does appear in the home screen, lock screen etc.

Simply, it won't play any sound or vibrate when Silent Mode is off and on respectively (that's how I set them up).

I have read everything online I could find and yes, I have enabled Alerts in Customise Notifications as well. It doesn't work.

I have tried rebooting and removing and re-adding the account. Nothing.

My wife has got exactly the same setup on her iPhone 12 with iOS 15.0.1 and also uses gmail as her only account with the stock Mail app, yet she doesn't have the same issue I have.

Any ideas?