Xbox Friends Cannot Join My Server

My friend on xbox (who is also playing on mobile) cannot join my Minecraft server. However, I can join his server. I'm thinking this issue might have to do with the fact that I recently backed up my iPhone. So I redownloaded my app and created a new world. But he could still not join my server. 

Any advice helps! Thank you

P.S. I actually have an iPhone Xs but it wasn't on the list