having the same issue and is repeatable.
I have found out that if you start a NEW world all players join without fail.. Its when they try to return to the game, then no one can join my game. We have now tested this on 4 worlds. 3 players all same issue, When they host or I host the problem is the same.
Host unreachable, and side note..... Map will erase itself on restart, so have leaving and coming back you map is blank.. Like the game, would love it if we could connect to each other..