LCD not working after teardown.

After a teardown (Lock Button Replacement), I have reconstructed the phone, but half of the lcd is grey. The touch function still works - i.e. I can tap in my passcode and use the keyboard under this blank part of the screen.

Ive since gone back, and ensured that all the connectors are connected to the top of the logic board - all to no avail.

Thanks in advance to anyone who can shine any light on this.