I know there are people having this issue right now when trying to create a new custom game so hopefully this will work. I’ve tested it multiple times already and it seems to work for me. If it doesn’t work for you but you know of another way that works best for you (until the OverWatch dev team fix it) then please reply with [SOLUTION] at the start of your reply so others can spot your solution.
The problem is simply this. While creating a new custom game the game will sometimes, if not always, give you the error message saying that the game is invalid and will not do anything until you “fix it” or discard the settings. Even a simple manner of just turning on or off a game type (like Skirmish or Deathmatch).
The solution that I found is this. If this happens, go to your PRESETS and choose any of the standard presents found there (I’d recommend Quick Play since that’s suppose to be the default preset that loads up anyways). After that you should be able to edit the game type without the “invalid settings” error. Again this works for me. Below is a YouTube video showing the solution as well as the bug.
Hopefully this helps a lot of people, if not everyone, dealing with this bug.