Try reseating the LCD connection, worked for me. Update: I sent mine back to lg for warranty repair and they sent it back unrepaired saying the motherboard was bent. As soon as I got it back I opened it up and reseated all the connections including the battery connection. Give it a try.
I had same response from lg, I believe it's a cookie cutter excuse because I sent my n5 in for repair for a blank screen and it was returned unfixed because of bent board. I opened up the phone when I got it back and reseated all the connections and the screen turned on.