If the drive light (left side of laptop) is lit or blinking:
Try shining a torch at an angle close to the laptop screen to check if you can detect any images when the laptop is on.
They will be very faint if they are there so trying this in a darkened room may help.
If there are images then you have a backlight problem, either in the display, the cable between the display and the motherboard or the motherboard.
If there are no images then try connecting an external monitor to the laptop and check if there is a display on it. Remember to press the 4th Action key from the left (rectangle symbol with lines either side) to toggle the display between the laptop and the external display or both on together. Even a TV can be used as an external monitor as long as it has HDMI inputs and you have the appropriate cord to connect the two together.
If the drive light (left side of laptop) is not lit or blinking:
I realize that you have already tried to do a BIOS reset but if still no good you may have to remove the battery and do a power refresh without it connected., i.e. disconnect charger, remove battery, press power button for 30 seconds, replace battery, reconnect charger, turn on laptop
Here’s the maintenance and service guide for the laptop (if it is a HP Pavilion x360 - 14-ba253cl that is) taken from this webpage.
Go to p.42 to view the necessary pre-requisite steps and then the procedure to remove the battery