However, when I package the game and run on 3 seperate computers with separate steam accounts I still encounter this error. Do I have to package the game as “Shipping” instead of “Development”? Not sure what I am missing for it to be non-debug mode for steam.
Also, I am using My own AppID, so problems with ID 480 shouldn’t be a problem.
Solution
To anyone that finds this: Turns out bAllowJoinInProgress is false by default. Once one person joined it considered the game in progress. If you don’t want people joining after the “lobby” level you may need a workaround as I don’t believe session settings may be changed after the session is created.