Can't accept Terms of Service

I purchased Spartan Assault recently, and it tells me to launch the xbox games app to accept the terms of service. The app launches but nothing ever happens. I’ve even searched for the Spartan Assault app and launched it there, and still the same issue. What am I doing wrong? I’m on Windows 8, so that’s probably the first thing.

Experiencing the same issue with Windows 10. Already wanting my money back here.