Could not create lobby due to an error
I am playing on the browser (Chrome and Firefox), when I try to create a custom match, a message box appears with the "Could not create lobby due to an error" message and won't let me continue.
I am having the same issue.
I've stopped using the game in a browser due to the many issues that happened. I'm now playing via the Steam client. There are many technical reasons that this could work better for you but since I'm not a member of the Admin staff here and have never seen their game code, I can't verify that this will solve your problem.
But I'd recommend the Steam route. It's worked better for me.