The traditional things that go wrong on a laptop display in my experience are...
- cable/connection becomes loose or broken. Try twisting the display gently.
- the inverter dies. Look at the laptop display with a strong light behind the lid and/or see if you can see the desktop faintly on the screen. Try toggling between built in screen, external screen and mirroring.
- display is broken after violence. Check for lines or jagged lines on the screen.