It doesn't let me in my friends' worlds and viceversa they can't join mine

I've tried to join my friends' worlds countless amount of times and I've tried to make them join mine but it won't let me, so I tried to exit and re-enter the game and I made my friends do the same and it didn't work, so then I tried to un-install and re-install the game multiple times still nothing, and even when i completely deleted my in game data it still wouldn't let me play multiplayer though i can join servers without a problem which is a bit strange in my opinion since it is much easier to join a LAN game than to join a server