After I create my party, click start game; the screen goes black but I can still hear the music playing. I've tried that various fixes here, but none of them work.

Can anyone help? I'm running Windows 10 Home 64bit.

I don't have any advice except to contact support. Be aware that they don't typically respond on weekends, they are in Poland and thus have business hours in that time zone, and they may take a few days to get to your request in the queue.

It's hard to get advice if you let no one know which game you are asking about.

Guessing based off capitalization: MM9.

Yeah, as Bookwyrm627 said, it looks like a case of a shift key held too long in the topic title. Unfortunately I don't know anything about troubleshooting MM9, but hopefully someone else can help.