If you try to play content through your iOS app you get a black screen with the loading icon that lasts too long, don't worry. Fixing this is often as simple as restart the playback and hitting the "Watch Now" button again. After a few seconds, playback should restart without any problems.
If the problem persists, check this help page in case it can be useful:
Due to our Terms and Condition, we remind you that viewing movies is not possible with a version of iOS that is altered by jailbreak.