Did you have an old HDMI cable? If not then if you are getting no sound at all (tv or audio system) then there may be a problem with the cable box. Try rebooting it. If you are getting sound on the tv but not on your audio system the cable box may be routing the audio only through the HDMI and not via digital output. You may be able to adjust this in the cable box menu. The analog stereo outputs usually work at all times.