Hi,
Have you tried pressing Fn +F7 when the laptop is on to see if this turns the screen on, or Fn + F6 to increase the display brightness?
Try connecting an external monitor to the laptop's HDMI port and check if it shows a display when you turn on the laptop. (you may have to use Fn + F8 to toggle between the laptop and the external monitor)
Can you detect an image at all on the laptop's screen if you shine a torch at an angle close to the screen when the laptop is turned on? It will be very faint if it is there at all.