Dear Users,

after some headaches i found a very simple solution for the nonworking co-op invite:

1. Only the hosting player is allowed to be in the game.
2. All other players should be not in the game.
3. Confirm Invite.

This solution worked for me. I hope it will work for you.

It worked for me too!

I can't believe it's impossible to invite someone while they are playing the game. That feature was present in games a decade ago!