My home theatre system wont work with tv?

my panasonic sc-pt170 dvd home theatre system will not work with my panasonic viera tv. it has a hd box built into it (my tv panasonic viera). have a hdmi cord, green, blue and red cables and yellow white and red cables which are all plugged into my t.v. but when i turn the viera link on to play through home theatre system my tv sound just turns off how do i fix it or do i need another box or something. my hd cords and red yellow blue green cords go straight from my dvd home theatre system to my tv. the picture stays but the sound just goes and i cant hear it anymore could any1 help please