I had same problem and answers above didn't help me. It turns out that new macbook pro's doesn't have power on pads anymore. The solution is: Shorting Pin #5 on the keyboard connection (#5 from the right with battery facing up) of the logic board to a ground point will boot the laptop. This is true for most late model macbooks and macbook pros from 2008~present. Some models have different ways to do this, however this will work for 90% of the newer unibody laptops. Found it from here: source of solution

The solution is: Shorting Pin #5 on the keyboard connection (#5 from the right with battery facing up) of the logic board to a ground point will boot the laptop. This is true for most late model macbooks and macbook pros from 2008~present. Some models have different ways to do this, however this will work for 90% of the newer unibody laptops. Found it from here: source of solution

I had same problem and answers above didn't help me. It turns out that new macbook pro's doesn't have power on pads anymore. The solution is: Shorting Pin #5 on the keyboard connection (#5 from the right with battery facing up) of the logic board to a ground point will boot the laptop. This is true for most late model macbooks and macbook pros from 2008~present. Some models have different ways to do this, however this will work for 90% of the newer unibody laptops. Found it from here: source of solution