Nexus Blitz Bug: no enemy walking nexus

I dont know how this happened, but in a nexus blitz game when we got to sudden death, the enemy did not spawn a walking nexus. because of this, we were literally unable to win. before this happened, we won bardle royal, and they won king of the hill and loot teemo. at the top, our nexus had health, but the other one was empty. neither team had gotten past nexus towers.