Laptop screen shows nothing what to do?

My laptop is on, so you can hear the fan and the button to turn on lights up, but the picture screen shows nothing at all, so 0 not even a black picture, it stays off completely, what can you do?

Did you accidentally switch to the external screen? There's a (device-dependent) key combination for this. If that doesn't work, the screen may be defective.

Detect and completely de-energize for 10 minutes. So also the battery out.