Question Laptop not turning on, but with steady green LED ?

Jan 21, 2021
Hi all, I am having some troubles with my Asus X551C notebook.
The context: it’s 6 years old and doesn’t have the battery. I removed it 4 years ago and from that day I started using the notebook simply plugged to the mains.

Yesterday: I pushed the power button and instead of the normal activation process there was a black screen (it was on, but black) with a blinking vertical red pixel line on the left border. After a few seconds, the screen turned off and the computer died, the fan stopped moving and there was no noise at all.
The only sign of life was the green power LED light, steady, without blinking.

I unplugged and plugged it many times, pushing the power button, but the computer didn’t turn on again, there was only the green light. A couple of times, apart from the light, the fans started to run constantly, but nothing more.

So I opened the computer and cleanead the dust with a manual air pump, but nothing, only the green LED.
After a few hours, I tried again and (miracle!) it turned on regularly and I even could do the last backup and a virus scan (no virus was detected). Then I turned it off and it definitively died, no noise, no fans, only -you already know- the steady green light.

What could be the problem?

Thank you so much for your help