LCD Lamp turns OFF during boot

[wingtips]

I found the HP Restore Manager and did a reinstall of win 10. It did not fix the problem. This is an HP T15.
Here is the situation. If I start the laptop with the external power applied, after the HP logo completes the screen goes black. It appears like the LCD backlight turns Off. If I remove the external Power all is good. Replacing the external power again shuts Off the backlight.
If I insert the external power with the backlight Off, press the Power button once, the laptop goes into sleep mode. Pressing the Power button again, the laptop displays the last page I was on and all is good.
I have set the controls to never go to sleep or turn off the display while plugged in.
I ran the HP Support Assistant and it did not find any out of date drivers.
I am at a loss, any suggestions?

[DavidSMP]

Hi @wingtips,

Good Day.  Thank you for posting your query in the HP community.  I read the post regarding issues with the computer going black when the charger is connected.  I will be delighted to assist you here.

Superb description and commendable diagnosis of the issue before posting. Kudos to you for that. 🙂

For better clarity and to assist you correctly, I would require more information regarding this:

• Please provide the complete model# or product# of the computer to assist you accurately.

Take care and have a blessed week ahead. 🙂

Cheers!