iPod touch screen will not turn on after replacement

My sister recently cracked her ipod screen and I decided to do a DIY repair. Removed the old screen just fine, and all the ribbon cables are fine and intake. I hook up the new screen and it workes fine, then right as i am place the new screen down on the double sided tape, nothing, no picture, no light, no nothing. What happen and how do I fix it, if it is at all possible?