What was the last thing you did to the phone? Did you recently flash something? Try booting into fastboot: power volume down, if it boots to that your savable, but not even the HTC screen shows up when turning on?
Sent from my Rezound using xda-developers app. CyanogenMod 11. S-off
Verizon HTC One M8
Liquid Smooth 4.4.4 Nightlies, Insert Coin
Main Wifi Device:
HTC OG Droid Incredible S-OFF: Cyanogenmod 11
Sadly A iPad First Gen. iOS 5.1.1 Jailbroken with GreenPois0n