I noticed when my surface pro 2 won't turn on even after doing the 30 second power hold and the volume up + power hold... when I taped the windows logo it would vibrate meaning the device had power but was just not responding... finally what seemed to work was I plugged in a usb device (mouse) to charge then I did the power thing, I also noticed the windows icon when tapped no longer vibrated, after a few seconds the screen flashed and it restarted.
Hope this helps someone.