Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.
This type of problem is often caused by a contaminated laser lens. You can attempt to clean it by blowing out the disc tray/slot area with a can of compressed air for dusting computers (keep the can upright only so you don't get chemical propellant on the lens).
If this doesn't help, you can try a specialty cleaning disc (example: Fellowes Blu Ray Lens Cleaner - click for link) which has little brushes that clean the lens more thoroughly.
If neither of these cleaning steps help, then this is more likely a hardware fault, which could include a bad laser emitter or pickup, faulty spindle motor or laser transport, bad d/a converter, etc. Any of these issues would require repair/replacement. If it comes to that, I can advise further.