I hit X. I place it on warrior I hit X. Nothing happens and the challenge still isn't done.

Class specific equipment? Wrong button? You tell me 😁

karui warriors are the npc characters you use in trial of the ancestors - shouldn't matter which tribe the item comes from.
you may need to equip it and use that character in a trial? not sure. never had any issue but also only play on pc

I just had to think about it for a sec.
I had to use it before placing them in the field.
Got it. Ty