I cannot add friends

This is a strange one. I am on playstation 5 and I tried to add my brother on xbox but it says no players match the search criteria. He then tried adding me, found my account fine and sent a friend request, I have not recieved the friend request. Thought ok maybe a coincidence, so he tried using another account and the same thing happened. Does anyone know why I cant see his account and his friend requests to me aren't goin thru??