You'll need to set the TV's optical output to "PCM" (A.K.A. "LPCM"). There should be a menu option for this as it's a fairly basic requirement. If you skip this step then the TV will switch between PCM for some channels and Bitstream for others. When it's on Bitstream you won't get any sound. So do make sure you complete this part as it is an important step in getting things working correctly.
