Players can't join game session

My brother and I are trying to play the co-op campaign online, on two separate consoles. We’ve invited each other to the game session, accepted the invite, but never get in the session. Is anyone else experiencing this?

Yeah everyone is. Most frustrating thing in the world. Can’t even play -Yoink!- campaign without dealing with unplayable bugs

sometimes everyone you want in your party will have to reboot halo then join up again. don’t try to invite or join a game until you have the game fully loaded and in the matchmaking lobby. sometimes if you get kicked out after a game, if you start up a match search by yourself, wait about 5 seconds, and back out you can then invite/join other players. its very finnicky, but those things have worked for me