My 2-month-old HTC One just bricked as described above. I left it unplugged overnight. Picked it up, and power read at 48%. Suddenly, The home and escape button lights flashed 3 times each, then the thing went dark. Now, no light when power is applied, no response at all.
I've tried the button pressing prescribed by Macronixx, to no avail. These HTC One buttons are tiny, and it's hard to know if I'm making an affirmative push. After 10 minutes during which I've held the power button for 60 secs straight while pressing no other buttons and holding also power + Vol_Up for 60 secs straight while pressing no other buttons. Nothing.
Now I'm trying the advice from the T-Mobile website: Plug it in to the wall charger for an hour, and the light should glow. (Patience!) "While still on the charger, press and hold the Power key for 15 seconds. If the issue persists, press and hold Power, Volume up and Volume down keys for 1 - 5 minutes. This process will re-calibrate the battery, and allow you to power on the device." We'll see how we go.
Nope. None of those funked up tricks are working, and my fingertips hurt from all that pressing (5 minutes!!).
Gotta take it back to the shop