iOS. AV Foundation. Why does AVPlayer work only over WiFi. No joy over cellular

In general I have been delighted with AVPlayer/AVPlayerItem/AVAsset. It works great for playing streaming music over WiFi. When I tested it over cellular - on the device as well as connected to Xcode - it refused to play any of my music streams. No apparent error is reported. The status looks fine. Just no music.

Is anyo开发者_高级运维ne else seeing this?

Thanks,

Doug