"Unable to connect to world" every time I try to connect to a friend's world.

So, this has been happening since the PS4 Bedrock update. Everytime I try to join a friend's world online (not server/realm), a message saying "Unable to connect to world" pops up. It happens on PS4, Windows 10 and Pocket Edition. I've tried everything; reinstalling the game on all devices, trying a different PSN and Microsoft account, checking my NAT, etc.

My friends cannot join any world of mine either.