Half touchscreen dead after Nexus 7 2nd Gen daughterboard replacement

So I have this problem, which is shame as I was well pleased with myself for swapping out the daughterboard (the usb port was borked).

Is it likely to be the either the motherboard ribbon (it has a crease in it close to the zif connector, although I tried swapping it around just in case)? Or the LCD ribbon? Or either not being correctly seated in the connector? They look fine but…

The screen was fine until I swapped the daughterboard, and I thought I was being pretty gentle with it, although presumably it could have been faulty to begin with. (Ebay from China somewhere).

Cheers in advance

Doug