Won't let me play with friends in multiplayer!!

It won't let me play with a friend on my Ipad!! I made a Xbox account and so do my friends and I tried to join their world but it didn't let me bringing me to a page of the grass block wall and saying something *I don't remember what it said at the moment* but I was able to join another friends world. then I tried showing them my world but they had the same problem!! they both have Android and I am on an Apple. I got the Xbox account to PLAY with them not have problems TRYING to play with them!!