Check to see if the disc is spinning. You can do this by one of two ways either
- a:) Listen for the disc to spin after inserting it or
- b:) Place disk in drive right way up (so that the label is not upside down). Load the disc and eject the disc again to se if the disc has moved i.e. the writing may now be upside down.
If the disc does not spin then it is likely that there is something wrong with the disc motor. If it does spin then the issue is more likely to be with the laser unit. Try cleaning the lens but if this doesn't help it's likely to be a more serious and ultimately more expensive problem.
Hope this helps