Touch screen not working after replaced screen & digitizer

The digitizer on the Fire 7" HD connects to the motherboard via a ribbon cable with a tiny ten pin plug mounted at its end. This plug doesn't seat very securely into its socket on the motherboard, so the engineers decided to hold it in place by a springy stainless steel clamp mounted under one of the motherboard screws. If you did not replace that clamp when you reassembled the Kindle, then the plug could have come loose. Also, the plug could have been damaged if it were plugged back in at an angle, or it may not have been fully or properly seated in its socket upon reassembly. If any of these conditions apply, then the 'touch' feature of the device will be lost.

If none of the above conditions apply, then, believe it or not, it is possible that your new digitizer screen may be cracked. Even a tiny hairline crack in the wrong place can partially or completely interrupt the touch feature. Examine the screen very closely to be sure; sometimes cracks are very hard to detect. One way to test the screen for hidden fractures is to rotate the Kindle so that the top of the display shifts to a different edge of the unit. Try to swipe the screen with all four edges rotated successively to the top of the display. If the touch doesn't work for ANY of the four positions, then the screen itself is probably OK (unless there is a crack right at the entry point which blocks all communication to the screen, or the screen was defective from the start) and your problem is internal.