Firstly check the security of the IDE ribbon cable at drive and motherboard.
or swap cables
If no suceess then
Problem: Disc is not recognized displaying 'disc', 'error', etc.
Damaged lens suspension or damaged lens cover preventing free movement.
Dirt, gummed up lubrication, or damage in lens drive mechanism.
Bad component in optical pickup.
Cracks in ribbon cable to optical pickup.
Need to adjust servo (or less likely, optical) alignment.
Faulty power supply, electronics, or control logic.
Cheaper to buy a new one than fix.