Dell Latitude e5450 no display

Hello,

My Dell Latitude e5450 laptop was working fine. I switched it off and literally minutes later I switched it back on and now the screen wont come on. I connected a external screen and all looks fine. I tried everything I know of but to no success. Pressing the Fn + F8 key does not work for me, I did the diagnostics tests etc. When I press the power button my keyboards backlight comes on for a few seconds and goes off and the Caps lock button flashes once when the power button is pressed. I would appreciate any help cause I literally tried about everything.

Thank you