I think your card is a fake (not by you). It has several issues I can see, no back plate, a single sli connector (so no HB-SLI connector which is standard for GTX 1080s) and it should have an 8 pin and 6 pin.
I would return it immediately. My guess is it is a GTX 960 that has been repackaged and bunk firmware to make it appear like a gtx 1080 in say GPU-z but you would have to hook it up to be sure. Which I wouldn't do as it may damage your system. Amazon is known for counterfeits and unfortunately i think you have been had.