Apple rejected Companion App due to platform limitations:
“…apps designed for developers to preview mobile app projects they are working on are not appropriate for the App Store.”
So you need to install it using TestFlight:
- Install TestFlight App on your iOS device: https://itunes.apple.com/us/app/testflight/id899247664?mt=8
- Then open this link to install companion app: https://testflight.apple.com/join/ruyYHU5E