Hello,
My friends usually can join my world in multiplayer, even after 2 weeks after the .40 updates. After that, suddenly they can't get into my world and i can't go into theirs, but i still can join servers. I checked the multiplayer setting as the article i found in support, they are what they supposed to be. I don't think it's the connection problem as well since we both already tried to do this for the last three days. I checked on the play store and the apps is up to date and my version with my friend version is the same as well.