Tech Challenged has AVR ??
 

I have a Sony xbr55a3, Denon 2310 and use comcast. Until today I only used the AVR(5.1) when playing dvds.. I ran HDMI from cable box to the Denon and out to tv. Toslink from cablebox to Denon and toslink tv to denon. Broadcast televison, premium channels works fine. Youtube works with the comcast remote. When honey uses the Sony remote to watch her knitting shows on Youube video ok, no audio ?????

I'm not sure what an XBR55A3 is, but you may want to remove the optical cable from the tv to the Denon and use ARC instead. Also, this may be a dumb question but in the internal TV settings, is the audio out set to "external speakers" (or similar)?

Denon 2310 does not have hdmi-arc. It makes no difference what setting I have the Sony set at .I did see that some sonys have issues with toslink

I solved streaming issues by installing the Nvidia Shield Pro. It connects directly to HDMI and allows you to add streaming apps.