If the disc isn't spinning, the motor might be dry. A tiny drop of electronic-safe lubricant (like white lithium grease) on the motor spindle can sometimes revive it.
Even tiny smudges can cause a "No Disc" error. Clean discs from the center outward in straight radial lines using a soft, lint-free cloth.
These thin, flat orange or white cables often wiggle loose. Disconnect and reseat the ribbon cables connecting the laser assembly and the screen to the motherboard.