Hmm. Not sure. Try this stuff:
Firstly, make sure you’re on a compatible device (see above).
Secondly, make sure you’re on the most recent iOS update. The app will only run if you’re on iOS 10.3 or newer. Learn how to update your iOS.
If those two things are done, it should work!
If it still doesn’t work, try the age-old method of turning the device off and on again. If you’re still having trouble, please email us at firstname.lastname@example.org.