When wanting to run solo challenges it'll say waiting for players despite pressing 'start solo' it'll stay on the screen and you are unable to cancel or press any buttons. The only solution is to clo...
Ideas
It happens when you skip the challenge cutscene too early and not all players (including you) have been teleported to the challenge start point yet. Just wait like 2 seconds before skipping the cutscene.
Good job figuring that out. I was about ready to walk away from this game for a while over that. Blows my mind that not a single tester of this game was the impatient type...