No touch screen, where to look for the problem?

Hi.

I have a waterdamaged Ipad 3 with a complete shattered digitizer. I took the whole Ipad apart and cleaned it first with propanol and then in an ultrasonic cleaner, put the thing back together and replaced the digitizer.

Now everything works (battery, lcd, boot-up) but there is no function on the touchscreen.

I double checked the digitizer screen with another Ipad 3 and it works fine. Also I checked the fit of the flexcable on the two connectors and they seat properly.

Any idea where to look for the defect?

Thank you very much!

Could it be that the connectors on the logicboard are defective? Is there any way to check for that?