No response from new touch screen

I have spent the last several weeks attempting to replace a faulty touch screen on my daughter's DS Lite. I have now tried two different brand new screens, both with the same result - when I put everything back together the unit turns on just fine but I can get no response at all from the touch screen. Even when I try putting the old faulty screen back on I get no response.

What could be wrong? I have been extremely careful handling the screens and their ribbon cables. I am pretty certain I am seating the ribbon cable correctly in its connector. I have seated and re-seated it many many times. Is there something else that can cause a complete lack of response from the touch screen?

Thanks very much.

SOLVED THIS PROBLEM MYSELF. TURNS OUT I MAY HAVE BEEN TOO CAREFUL SEATING THE RIBBON CABLE FOR THE TOUCH SCREEN. TODAY I THREW CAUTION TO THE WIND AND RAMMED THE CABLE INTO THE CONNECTOR, THEN PUSHED IT IN EVEN MORE USING PLIERS. I HAD STOPPED WORRYING ABOUT CREASING THE CABLE AND JUST PUSHED IT AS HARD AS I COULD. TO MY SURPRISE, IT WORKED. MAYBE NOT THE RECOMMENDED METHOD, BUT THIS DS IS NOW BACK UP AND RUNNING.