Surround sound from Sky +. I have set up a Yamaha RXV361 AV receiver with Tannoy EFX speakers and

Question

I have set up a Yamaha RXV361 AV receiver with Tannoy EFX speakers and connected the Sky+ with digital optical and DVD with Digital coaxial. When I play a DVD sound is fine from all speakers. When I watch sky+ sound only comes from front R & L speakers and sub woofer. Any suggestions how I rectify this? i just bought a Yamaha RX V361 and can not get the surround sound to play with TV, it only works with DVD's