touch screen is unresponsive

Hi, the touch screen on my Ipad4 doesn't work, I have checked the cables to the mother board and are all fine, even tried a new screen but still not working, have tried holding the sleep & home button down to re-boot but nothing, I was going to try and do a complete factory reset in itunes, when plugged in, it says in my computer "do you want to allow this computer to access information on -----Ipad? I click on continue and then it says "To allow access please respond on Ipad" but I cant respond on Ipad because the touch screen doesn't work, any ideas anybody