replaced crack lcd with a colored lcd it doesn't turn on.

I repaired a cracked screen on an ipod touch 4gen. I plugged the lcd assembly and tried to turn it on, the screen was blank no response at all. I disconnected the lcd assembly and connected the cracked one and it did turned on. Since in the cracked screen the digitizer didnt work so i disconected it while the ipod was as sleep and connected the new lcd assembly and it works, everything works. I turned it off with the new lcd assembly connected. It turned off ok but when i try to turn it on no response, no power... please help cause this is driving me crazy. I have plug and unplugged the digitizers many times and the same issue... i even got another screen and still get the same issue.