HTC U11 Turned Itself Off and Not Booting

[supersophisticated]

So, I am on the Stock U11 ROM unrooted and on Android 7.1.1.

The phone was charging by my side, on my desk.
It reached 100%, but I did not unplug it.
I had the keep screen on while charging setting, turned on.

After about 30 minutes it turned off. I noticed the green notification light (fully charged indication) had turned off.
And when I checked, the phone had turned off. By itself.

Now I am trying to turn it on, nothing happens.
I try to hold the power button (for ~30 seconds) to force a reboot, nothing happens.

Can anyone help me. It is under warranty though. So, I will contact HTC about this. But I wanted to check if there are others that faced this same problem.

Thanks

 

[schmeggy929]

Try power button and volume down

 

[supersophisticated]

Try power button and volume down

I tried that, no good.
I tried Vol Up + Vol Down + Power too. No good.