iphone 13 pro max with update ios 15.3.1 will not do anything if not connected to wifi except make phone calls

How do I fix settings - my husband's phone can't imessage or load apps in 5g? My husband updated his ios to 15.3.1 and he can't run apps or imessage away from our home wifi. I did NOT update the ios (15.3) on the new phone and it appears to work fine without wifi. We have cellular data on - both phones have the same settings. The main difference is he updated to ios 15.3.1