I own the new HTC One M8 and had the same issue happen to me last night while my phone was charging. It died and never turned back on even when I left it charging over night. I tried using different PS, cables, and a USB batteries to troubleshoot on my own. I found that the charging port was not active and that my battery wasn't charging at all. I thought my phone was bricked after only having it for a week.
I just contacted HTC support and after a few lines or chatting, my phone is up and running again.
Just in case others run into the issue, I'm sure they'll look here first.
HTC Tech support told me there is a way to reset the communication between the phone and battery by holding down the power button, vol+, and vol- for a full 2 minutes then releasing all buttons. The phone will wake up on its own again and charge, if not attempt a normal power up shortly after. This worked for me.
HTC One (M7) users try this as well and report back if it works as well. If this method and all other methods do not work, contact support they'll either have a solution or have you send it back for diagnostics/repairs.