This seems to be recurring problem with no solution. "my rx480 from xxx is not being detected by anything" And I just joined the ranks.
(EDIT)I unfortunately had to return all of the compuonets but if you are having the same problem please feel free.
https://www.reddit.com/r/AMDHelp/comments/4qhl3o/rx_480_isnt_being_detected_after_installation/
Mother Board: ASUS M5A78l-M/USB3
CPU: AMD FX 8320E
Memory:oh god its from korea(10gb total[2x4 1x2])
GPU: Radeon RX480 DUAL
OS: was HP windows 7 but "upgraded" to 10
So here's the problem. Brother wanted to upgrade his old HP pavilion. from a XFX R7700 in favor of a new rx480 from ASUS. We also got a new mother board from asus and cpu. so I disabled the old device in device manager slap his new parts together and into new case and the card isn't being detected, By anything. I like most have tried a ddu to no avail. So whats the problem.