Friend's game closes to desktop on server join

i am wondering why my friend is not able to join my server even though i have modified the config so that they should be able to join the game forces him to desktop

 

It sounds more like he has a problem with the game starting and not the actually joining the server

 

Friend had this problem, Delete the game, restart your computer, then install again. That should work as it did for him. (Restart just makes sure it is really deleted)