Multiplayer not working/

[RadSlime]

So today I was going to try out the new grounded game with one of my friends. When I went to create a lobby I got an error message that said "There was an issue hosting a multiplayer game, check your connection and try again" I tried again, and I got the same message. I've been trying to figure out why it won't work for a while now, I've even went and looked at forums where other people were having the same problems as me, and tried what fixed the problem for them. It still didn't work. I've tried to get my friend to create a lobby, which he can. But I can't join. Does anybody know how to fix this?