I have some 980ti, connected 3 monitors, (2 trough dvi one with hdmi) and all works jut fine.
If you can plug monitor to motherboards integrated chip, do it, power pc.
see if that graphics card is detected, if there is no error. I think nvidia control panel will show you if there are some errors with card.
You should get second montior at least for testing.
Also are you really sure you connected those 2 additional power cables on top of card? Mast of time i am forced to use adaptors to convert poer lines from 2x3 pins to 2x4 pins, sometimes powering both adaptors from same psu line is not enough, they sometimes need 2 different power lines from psu. So make sure those additional power cables have connection.
I also would remove card from pcix slot check if there was nothing broken when you put it first time. And try another pcix slot.
Eliminate all other possible causes for malfunctioning before you send card back:
- make sure additional power cables are connected and give power (would be great if you could borrow another nvidia card and see if it works)
- check this card in different pcix slot, there could be some of those small contacts that does not work inside slot.
- see if card is detected at all in nvidia control panel
Ps. do not lubricate that pcix slot or edge of card. My friend did it, contacts are shiny and do not oxidate, but when he sneezes his card pops out from slot.