I've been trying to play multplayer but it says that it wasnt possible to connect to the world

I have been trying for a while to play multplayer but every time i click to enter my friend world it says that it wasnt able to connect to the world. the first time it happened he had the same prblem not being able to connect to my world, but this time he says that i wasn't even online for him and for me it still have the same issue.