Ok so if I understand you when you try one of the 2 6 pin the system turns on but since the card needs both the video does not work. Then when you try the second 6 pin either with or without the first 6 pin the system does not work. If this is correct you have a defective power supply. Though it may be new sounds like you got a bad one. Return it for a replacement.
you dont know how much this means to me
, been trying to figure this out for a while now!