Spec won't have changed. Still could be the cable, but age shouldn't mean it's deteriorated in any way. I've got a cheap one that's 14 years old that still works fine.
Getting a new cable is the next to do, even if there's nothing wrong with the one you have; unless you have something else you can try that to confirm whether the issues lies with that or elsewhere. Nothing fancy as long as it works.
If it's not a cable issue it could be a fault with the DAC itself, but you can't determine that without knowing if the cable works for certain.
Edit:
Have you anything else you can try the DAC with, like a DVD or BD player with optical output; or even a TV?
If you can, and still get nothing, then it's either the cable or a fault.