Stand alone SE 3 watch mail app doesn’t access gmail

I have a stand alone cellular watch for my son, an SE3. I have his gmail account setup thru the phone app, but on the watch in the mail app, it doesn’t allow him access to his inbox. I’ve deleted and reinstalled the gmail account multiple times, rebooted watch and phone. Phone and watch have latest iOS 26.0.x. All nothing. What am I missing here?