When I use Airplay to my Apple TV some podcasts just won't play. My Apple TV is connected to my amplifier and the TV, often I don't have the TV turned on and I'd expect to play through the amp for an audio podcast. All I see from the ipad or iphone is you hit play in the podcast app and it just doesn't start.
I happened to have the TV turned on the other day and saw there was an HDCP error message on the screen. Obviously that's nonsense, the podcast should play via Airplay or on my ipad just the same.