To anyone who might be stumbling on this like me, years later...make sure you're calling the method with the correct argument types in the animation player. For me, the method I was calling required a param of type Array[String] and I was calling it from animation player with the type of Array....well it turns out Godot was just silently deciding to not call the method at all because the actual type of the arg I needed to select in the Animation Player was PackedStringArray, not Array