New GPU Issues, AMD 480

[Moosehed]

Tried to upgrade my currently computer's GPU as mine has been having issues. Bought a Sapphire Nitro RX 480 8gb card. I've ran driver sweeper before install of new card to wipe my old drivers, installed new card. When computer turns on, GPU has power, lights up and fan on, but cannot get any video out of DVI or display ports. Haven't tried HDMI. I have tried removing and installing my ram, make sure card is seated properly, all connection secure. I tried installing drivers for new card, then installing card and that didn't solve the problem either.
Old card works the same before and after replacing the GPU.

Any help or advice would be great.

My Build
Processor: i5-2500k Sandy Bridge 3.3Ghz
MoBo: Gigabyte GA-Z77-D3H
PSU: Corsair 1000w
HardDrives: 240gb SSD, 1TB and 500gb HDD
RAM: G.SKILL Sniper Series 32GB (4x8GB)
Old GPU: AMD HD 6990 4gb
New GPU: RX 480 8gb

[Thunderball]

Did you connect the additional power?

[Purpleisbetter]

It's power related.

Auxiliary 8pin plug not connected or simply faulty card.