The optical out signal with any Toslink fiber can be seen at the end of the interconnect as a red light. So if you plug in the connector to the TV.. and have it supposedly sending the signal... Can you SEE the red light at the other end of the cord? IF not, then there IS NO SIGNAL being sent.
Are you certain it is a optical output??? on the TV?
If you DO have a signal, the red light... Then I would bet your TV is not making a PCM compatible output.
Sadly there are all sorts of digital outputs, many surround, most of them incompatible with two channel DACs.
One other possible solution (IF you have a signal... the red light) from the TV, is to use a cheap receiver just to convert the surround signal from the TV digital to one you can use. Some receives can take in a surround digital signal. and output a TWO CHANNEL PCM signal.
If it is not two channel.. it still is not going to work with a stereo DAC.