* Missing pins on the touch screen connector on the logic board, this will be obvious when inspecting them for missing pins
* Crushed digitizer cable, the cable bends in a way that it does not get crushed by the housing on the iPad between the glass. When closing it up there is a spot where it can get squished which ruins the digitizer cable.
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If it is the latter the screen will need to be replaced.
Usually it comes down to two things:
* Missing pins on the touch screen connector on the logic board, this will be obvious when inspecting them for missing pins
* Crushed digitizer cable, the cable bends in a way that it does not get crushed by the housing on the iPad between the glass. When closing it up there is a spot where it can get squished which ruins the digitizer cable.