Strange GPU power problem

Just built this budget gaming pc for a friend and I cant get the gpu to power (fans dont spin, no signal to monitor) I thought maybe it was a bad card or PSU but I tried the card in my computer and it ran fine, I then put my 7970 in the new build and it ran fine so its not an issue of not enough power either. Im stumped. Heres the specs

ASRock H77M LGA 1155 Intel H77 HDMI SATA 6Gb/s USB 3.0 Micro ATX Intel Motherboard
GIGABYTE GV-R787OC-2GD Radeon HD 7870 GHz Edition 2GB 256-bit GDDR5 PCI Express 3.0 x16
Antec NEO ECO 520C 520W Continuous Power ATX12V v2.3 / EPS12V 80 PLUS Certified Active PFC Power Supply
Intel Core i3-3220 Ivy Bridge 3.3GHz
G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800)

Any ideas?