Power button is on, the laptop is charging, but nothing is there in display

[Ag20234]

When I am pressing power button in my laptop, it is glowing. My laptop is charging, also there is power in usb port, I have checked. Nothing is coming on the display in the screen. It is totally black. There is no issue in the display  because I connected another monitor with hdmi cable to my laptop, there was also no display at all. 

[WAWood]

Here's a video from HP Support about diagnosing the issue of the laptop starting but having a black screen instead of any display:

https://www.youtube.com/watch?v=sj6kYmT7GLs