"Who takes care of him?"
Translation:Kdo se o něj stará?
I am learning, too, but I think your first version should work. Try reporting it, if it doesn't.
Your second version probably would not be accepted, due to the placement of "se."
Kdo se stará o něj (no accent above o) is fine and we accept that. The second one I guess you miss typed kde instead of kdo, but it still would be super super archaic and nobody would say it these days.
As a rule of thumb, the second position is where you should put it, unless there's a conditional "by" - in that case, it takes the third position.
Who take care of him? = kdo o něho se stará? and not Kdo se stará ó něj? (of her no of him) !