Artorias of the Abyss DLC availability

So question, started up a run of Dark Souls. Had the game for years but this is the first time I've really made a go at it.
Much too far in to stop now (lvl 80+). Playing the DS 360 version via series x. Was hoping to get the DLC but says it's unavailable both on console and through accessing it on PC. Any way to make it happen or am I outta luck?

Please and thanks