I have a HDTV plasma TV about 7 years old that does not have an HDMI outlet. I also have a Panasonic SC-PT480 surround sound system/theatre connected to my TV, which works great for DVDs. I wanted to add a Roku box to my TV so I can stream videos and connected everything successfully except the sound. I can hear the sound through the TV but not through the surround sound system.

I have a HDMI cord connected for the Roku box to the surround sound but no sound. Please assist if able.