Cannot join worlds, just sent back to title screen upon joining a game, other than newer worlds.

Cannot join worlds, just sent back to title screen upon joining a game, other than newer worlds. This is happen to me and my friends, starting a few days ago. we cannot join each other on our normal worlds, just newer ones. We also cannot join other peoples long running worlds. Our NATs are fine and still set to moderate. We have tried everything, even reinstalling the game. 

The only thing working is my friends girlfriend can join his world as they are in the same house on the same internet.

We have not been able to play, and have had to switch to other games.