I'm having a problem playing a Youtube video on my iPhone 5, iOS 8.1.2 (had problem prior to this iOS version too, but it worked a few months ago).
It plays fine if I open the app in the phone's browser, but if I "Add to Homescreen " then launch the app from the icon, the video will not play (the whirligig spins and eventually times out to a gray play button, if you try to navigate to another page the webapp crashes).
I can duplicate this from a fresh app. Can you duplicate this problem?