Friend who I invited to my realm is not being let in the world

So I just today made a realm, and I invited my friend, so he joined the realm, but once he tried getting into the world it said unable to connect, his wifi was fine too, nothing was wrong and it wouldnt let him join. Please fix this I literally spent 8 dollars mainly for me and him, and it wont work, other people I invited are able to join, I'm on android, he is on ios, other ios people were able to join but not him.