My left side (around 15% towards the edge) of iPad 2 has become unresponsive to touch, after I replaced with the wifi antenna. I checked the digitizer connector cable and it fits ok in the connector on the motherboard inside the iPad. I can pull it out and back in again, and it is the same result, so I don't know whether I should buy a new digitizer, or perhaps something in the motherboard is broken. How can I check this, anyone?
Sadly the best way to check would be with another whole display assembly. It sounds like it could be the actual digitizer layer (sits under the LCD display that is covered by the gorilla glass) or at least part of it that's broken. If the cable was the issue if expect the whole display to stop responding to touch. Good thing is the part is easy to find, ifixit should be able to help with that and any tools you might need.