It could one of several things.
First was the power switch still on and the battery plugged in when you detached the original screen?
This could have caused a small surge and blown out a micro fuse or some micro electronic piece. Its located near the digitizer cable. You would see a small scorch mark there. You will have to run a jumper to get it to work. Just bypass it with solder.
Second you could have the wrong digitizer. There are several models. Make sure the part number matches the old one.
Third. the cable could still not be in all the way. check this first. It shouldnt need any type of software upgrade or update to work.