Oh also, I’ve found - forget the Stand Alone - I have never got it to work.
I use the Staged Build and ensure you’re running steam and logged in (as you probably already are)
Warning: this makes debugging extremely painful. You can attach VS to you’re running package process and break into C++, but I’ve not found any way to break into blueprint:
So I’ve moved all difficult code to C++. But the JoinSession node DOES work. Either your config is wrong, or using Stand Alone is your problem