Serviio

Hi, I've just installed Serviio on my Mac and my Samsung UE55C6005 found it without any issues. However I can only get sound out of my TV speaker as oppose to through my Onkyo TX-NR609. All are connected via HDMI. I know it's probably something simple, but I just can't seem to figure it out.

Any help is greatly appreciated.

Cheers.