Hmm, I'm not using the mod myself, but it looks like it's an ESP-based replacer, that is the ESP switches records from the old resources to the new ones in the game.
This isn't about new options to hair choices for certain races, so other race-changing mods loading later mostly shouldn't be undoing it. Only other mods changing the same hair records will.
But does it change Vanilla game hair records now or OCOv2's?
Whatever, it doesn't seem to be an installation issue (replacement files not in proper places or for other reasons not replacing their originals). A plugin conflict would be the most likely culprit, so either faulty load order or requiring a bashed patch which isn't properly set up yet.
(I was always a little perplexed by what OCO's page listed as "incompatible mods", knowing full well myself a properly configured bashed patch, and maybe some missing Bash Tags fixed, can definitely make it work. But these last years I anyways got a feeling people no longer know what the bashed patch is about and what all it can really do, if configured properly. What with all those "compatibility patches" of late, fixing incompatibilities with another ESP each, which a simple bashed patch inclusion could've fixed just as well? Is knowledge really getting lost for good here?... Ah, forgive my rambling.)