Blunder Policy does not activate if a one-hit knockout move misses, if Triple Kick, Triple Axel, or Population Bomb ends early by failing one of their subsequent accuracy checks, or if a move misses due to a target being in the semi-invulnerable turn of a move. The Blunder Policy only activates if the move misses, not for other reasons it might fail to affect a target (e.g. immunity due to type or Ability, being protected by a protection move, etc.).
Blunder Policy (Bulbapedia)
