From MLB.com
Restore
Subscribers who have made an in-app purchase through Apple iTunes on a mobile device will use the Restore button on the paywall, for example, when re-installing the application on an existing Apple or new Apple device. A restore can only be completed on devices which share the same Apple ID as the initial purchase. Prior to attempting to Restore an Apple iTunes purchase, please go to the At Bat "Settings>MLB.com Account" section and ensure that you are logged out.
An Apple TV in-app purchase cannot be "Restored" to a mobile device. An Apple TV in-app purchase must first be "connected" to a MLB.com account for portability in order to access subscription features on compatible mobile devices by signing into the application with valid MLB.com credentials.