iOS version on 12.5.5 now and the "AppGameKit Player" (from the App Store) still does not work. The splash screen pops up but then quits. I've updated the github issue thread to hopefully bring attention back to this.
My own apps created in AppGameKit Studio work fine when pushed to the iPhone adhoc or published to the store.
I tried to export the AppGameKit Player from the IDE following the instructions in the readme.txt file which says "export the AppGameKit player using Tools->iOS->Export AppGameKit Player" but that menu item does not exist. Is there a way to export just the Player App from the Studio IDE so I can push it to my phone manually to see if it works, instead of using the version from the App Store?