No notification sound on my iPhone when someone rings the doorbell

I have chosen a sound in the app, sounds and haptics allows for calls on the iPhone to come through even in do not disturb, volume on the phone is up, notifications for the Ring app are allowed in iOS settings.  But the phone doesn’t vibrate or make a sound. If I look at the screen I can see it’s calling… but I am not constantly looking at the screen.  It’s fine when we’re home because it comes through an Amazon speaker but when we are out and want to talk to someone at the door it is pretty impossible. Any ideas what I’m doing wrong?