When trying to join a friends online world, I get an error saying unable to connect to game with no explanation as to why. I have tried this with multiple different friends and worlds and cannot join any. They can also not join mine. I've never had this error before, can you help me?

I have seen lots of different 'fixes' online but none seem to work, and I cannot change the nat type of my PS4/router. For some reason if we start a new world in the old edition of minecraft we can join each other, however in the new version we always get this error. Nothing in my internet settings has changed since we last played, but now we can't join each other. Is there a way around this?