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
HTC Rezound:PAC-Man 4.4.2 With SENSE!, Cyanogenmod 11, Sense 5
S-OFF using Rumrunner.
TWRP: 184.108.40.206/PhilZ Advanced CWM
iPad 1st Generation Jailbroken with Green pois0n . iOS 5.1.1
Droid Incredible: Stock (not for long hehe)
HTC EVO 4G the Original OG 4G: Everolv 4.2.2 ;D