LCD does not turn on.

Hello! I will describe my problem shortly. This afternoon I replaced the digitizer because it was broken. The glue of the broken digitizer covered a part of the LCD (the frame) and the lcd went out from its slot when I separated the digitizer from the rest of the body. In this case I had the small LCD from an hand and its slot (the part in which you collocate the chip with camera etc) from the other hand. The problem is: when I mounted all the pieces toghether even the new digitizer all worked fine except the LCD that was black (the phone turns on I'm sure of that)

How is it possible?

Thank you