Screen Goes blank when making call after Digitizer Replacement

Hello all

I have recently replaced the digitizer on a Nokia Lumia 820 (aftermarket part not original).

All is ok except when I make a call the screen goes blank and doesn't come back on again, I can hear the person im calling and they can hear me, however the screen doesn't come back on when the phone moves from the face.

Now Ive moved whatever little parts I can from the proximity sensor area of the old frame (the phone works fine in the old digitizer) and transferred to the new digitizer.

Can anybody advise please

Regards

Ali