Hi and welcome to the forum.
Being technical is no reason to struggle, we are here to help. The other day, I had to explain to my parents that system updates are not viruses.
The easiest way to have a look into this is the cable itself. Optical cables are made of very fine strands of glass and depending on how they are handled, ie folded they can snap. The first thing I would do is plug the cable into the back of the Cocktail and the other end have in your hand and point it at a surface. It is not a blinding light but just in case.
Since it will emit a red right from the end that is not connected, you should that end light up a solid red If that is the case, the cable should be ok. Thenmake sure it is plugged in. Usually they click a little as you do it.
Once done, you may need to press the Input - or + button on the surround sound remote to get the right input.
I would try the above and let us know how you get on.
Regards
