Thanks Kruffty
We got it working but in a strange way
we set the serverconfig as "survival" and then we create versus play with friends lobby in the game, and point it to the steam group server, and then all have to join the lobby before we start, and then when we start it, we end up with a 8 player survival game, but nobody can join after the game is started
could that be a only join trough lobby line I have to write in cfg and disable