Replacement LCD not working, rainbow colored vertical lines

My original LCD cracked so I ordered a new LCD for model A1286. Having replaced the LCD I now only get a white background with rainbow colored vertical lines covering most of the center of the display.

Concerned that this was an issue with my disassembly I reconnected the old (cracked) lcd and it is still working perfectly (apart from the crack). Therefore I don't consider this to be an issue with the connections.

Connecting to an external monitor still works. I also tried resetting the PRAM and PMU but makes no difference.

Any advice for next steps would be greatly appreciated.