The HT-C6930 (U.S. model) doesn't have ARC, and I think it's that way feature wise in your region also (although, the Samsung customer service center should be able to clear that up if there's still a question).

The TV is right, the cable is right, but the HT system doesn't support ARC, and all three components needs to be able to take advantage of that technology.

Optical audio would be the next best thing.