User blog comment:McLarenP1 Boy/ReplayKit Rant/@comment-25051390-20170722221711/@comment-25051390-20170724022607

Regrettably, neither Window Capture nor Game Capture work well with Windows Store apps.

You must add a Monitor Capture as a source to a scene and use it to record a Windows Store game. You can still use the "Sub-region" feature to limit the region of the entire display captured.