The cables are one of the most sensitive parts of the repair, but in my experience the edges of the LCD (especially the top edge) are very fragile. If you put any pressure whatsoever on them (even while the metal heat shield is on) you can do irreversible damage to the LCD or the digitizer, or both!
So in summary: while the cable might be bad, you could have done something to break the digitizer during the repair.
1. I would try putting the old screen back on to make sure it's not the board.
2. Try the new screen on a different phone (if you can).
If the old screen works, then the new one is broken. If the new screen works on the other phone, your phone is probably broken, especially if the old screen doesn't work on it either, and definitely if the old screen works on the new phone.