Hori Real Arcade Pro V Kai- Working in PC & 360 but not XOne

[gameoverDude]

I recently got an Xbox One and the HRAP V Kai. The issue I am having with it is that it isn't working on the Xbox One, even when the switch is set to ONE mode.
Just to confirm that everything else was fine, I tried it out on the PC (MAME with Battle Garrega & Ketsui) and 360 (Contra & Black Knight Sword). In these two cases it worked. The Xbox One didn't seem to pick it up, so I grudgingly used the pad to play Raiden V.

Any ideas what could be the deal? Thanks in advance.