Can't connect to World

When my boyfriend and I attempt to log into a world, the person who joins the other can't enter the world, it just says connecting to world and then unable to connect to world as an error. I play on Windows 10, he on Nintendo Switch. We were able to play together once, and it worked. I'm very frustrated because I bought the game twice just so we can play. So I'd like this issue solved. I'm aware that this issue was brought up, but apparently never resolved. From what I've researched this issue has existed for over 2 years.

Best regards from both of us,

Cedric and Florian