Se requiere la inicialización explícita del SDK de Audience Network para iOS.
Después de configurar el SDK correctamente, debes inicializarlo.
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
FBAudienceNetworkAds.initialize(with: nil, completionHandler: nil)
// Pass user's consent after acquiring it. For sample app purposes, this is set to YES.
FBAdSettings.setAdvertiserTrackingEnabled(true)
// Your app initialization logic goes here...
return true
}