That is almost always a bad IC on the digitizer. Try a new digitizer and it should work. If not, then there is a chance you knicked or tore the power flex cable. The flex cable is dirt cheap to replace but does take some patience to get installed. Pay attention and take pictures when you are removing the old one.
The easy way to figure out which one is your problem, hold down the power button. If the "slide to power off" shows up, its the digitizer. If nothing happens or the screen goes dark, its the power flex.
Good luck