Some questions.
1) Did the player ever work?
2) Can you reseat cables / connectors and try again? (is it in a notebook or tower machine?)
3) A rare solution: is the disk upside-down? Seriously, there was a poster with a slot drive which had been installed upside-down. Putting the disks in the other way solved the problem.
4) These drives fail. It may need to be replaced.