This would most likely be caused by an audio connection issue. To determine if the system is getting a signal from the TV you want to check the LED status:
With the system on, press and hold the Mute button on the remote for 6 seconds. (Note: The system LED flashes after 3 seconds indicating Dialog Mode on/off; continue holding mute for an additional 3 seconds until the LED changes again, indicating Diagnostic Mode.) Release the button and determine the LED blink pattern
To exit Diagnostic Mode, press Volume + or - on the remote
You should see an alternating red and green signal from the system. If you do not there is most likely a bad connection or cable.