Unable to connect to world

When ever I try to join my friends it says connecting to multiplayer game and then comes up with “unable to connect to world” with no explanation or help, we have done everything like restarting our iPads and phones and deleting it and reinstalling it and we both have perfecting fine WiFi and it still won’t work! It’s very frustrating as if we want to make a world together we can very rarely join each other.

:)