Either it isn't connected correctly or the ribbon cable may have been damaged when you put it back together, it can tear VERY easily. This would cause the touch to stop working.

Open it back up and make sure all the cables are connected.

It's also possible the logic board itself has a damaged port, but confirm that it's not the digitizer screen itself.

Make sure that the Digitizer ribbon is clicked in all the way, that was the problem for me.

If the ribbon cable is plugged in good, make sure you reboot. It is about like the screens, the ipod has to reboot to see that it is connected.

try restoring the iPod touch.

maybe the touch screen has been damaged during yout operation or there is a loose connection

how did you know that this was the problem with the touch screen? the "black resistor" I am having the same trouble with my touch screen. I have restored, rebooted, bought 3 different model screens, tried gorilla tape to hold down a tight connection, used 90% alcohol to clean the insides everything. Everything is working find on the ipod except I can't get the touch screen to work and it's driving me nuts!

i figured out why the touch screen isn't working or responding, this is cause by static tiny rectangle black resistor is blown out, located on the upper pcb right between the square metal and

square plastic(like diamond)

and it is impossible to fix it ,