Explain further what is not happening
is it not reading or not wrting?
If it is a new drive- did you install it or is the PC new?
If you installed it simply make sure the ribbon cable is fully connected both ends.
Use a CD disc drive cleaner[A fiver in most Superstores] its a disk with a ittle bruch and a tubs of fluid.
And of course if all else fails at only a few months old - take it back.