@Rosslyn0, when you say "I had cancelled a New Years Eve weekend..." does that mean you cancelled someone's confirmed reservation for New Years Eve weekend?
If so, then your can't unblock those dates on your calendar; the blocking of those dates is a consequence of you cancelling a guest's confirmed reservation (if that is what happened).
The only people who can unblock it for you is AirBnB. You can contact them and tell them your story and see if they will make the change for you.