portion of screen not responding to touch

I replaced the battery in my 23013 Nexus 7 and when I put the device back together everything works except the bottom few lines on the screen (top being the side with the control buttons) do not respond to touch. When I rotate the screen the same area of the screen still fails. My screen had a crack in it before I did this and it worked fine. After replacing the battery I then had the screen replaced and the device still failed as before so it does not appeAr to be the screen itself. Any ideas how to proceed on this>?