I have a world in which I played with a friend via Xbox live, we play in the betas so that we find and report bugs. We were able to play normally with me hosting and he joining. But now it is imposible for him to join. No changes were made, same android version, same network, same phones, we only updated to 1.16.200.51. This problem came within the same time Java acounts started migrating to microsoft so might be related. Minecraft has become a single player game now.