Firstly, confirm that all brightness levels (usually a keyboard function) are correct
Next plug in an external monitor, to confirm all software settings are correct
There may be a toggle function button, on your laptop to select external monitor
Or just start the laptop with the external monitor plugged in
If the external monitor works
Then you have a hardware fault with your LCD screen on your laptop
In most cases this is the Inverter board (electronic board in screen area)
You would need to dismantle the screen to locate this part
At which time, you could also check all internal connections
Note: This type of computer servicing requires an experienced person, who will need to follow all power and anti-static recommendations
You may also need to locate the dismantle guide for your laptop (if exists)
