Roaring Moon ex Frenzied Gouging did not KO Noivern ex

In a match I played, Roaring Moon ex did not KO Noivern ex after using Frenzied Gouging attack, and after Noivern ex used the attack that blocks all damage from basic Pokemon. This attack does not use damage, but is an instant KO. The attack also did not apply the 200 damage to Roaring Moon ex, the attack just did nothing.