free client screen hangs when joining my custom game

I'm trying to play offworld trading company with my 2 kids both on my same network.  I bought the game, and they both have the free client, and their own steam account.   One kid is able to join my game normally and play, the other one just gets the background screen, and nothing else pops up when they try to join the game.  It shows them as "unready" as if they have joined.  I have tried turning off firewall on their machine.  I have also tried uninstalling the game, and reinstalling it, and neither helps.

Update: He's also unable to join "ranked", it says that his client isn't connected to the tachyon servers, however he's definitely online, and on steam.  I tried deleting ALL files, including those within the documents folder, and reinstalling, and it didn't help.  I seem to remember it asking about some option of whether or not to use some stardock service when they first joined the game.  I wonder if he selected a different option than we did?  How do I reset this, or change this option, if that's the case?