It could be either, but if you look at the customer reviews you will see a number of people have had problems with this cable due to the length.
At a guess, the cable is not a "top quality" cable and your system may even be very slightly out of spec (maybe voltage?) as well, so the cable is not working.
Its possible a higher quality cable will work.
If you want to check if the cable is broken/doa, you can always get a multimeter out and test each set of pins.