Estoy integrando la notificación FCM y la mensajería en la nube en mi aplicación. He seguido exactamente los mismos pasos mencionados en Firebase doc. Incluso lo he intentado con un código de muestra proporcionado por FCM. solo arroja algunas advertencias como<FIRInstanceID/WARNING> Failed to fetch APNS token Error Domain=com.firebase.iid Code=1001 "The operation couldn’t be completed. and <FIRMessaging/WARNING> FIRMessaging registration is not ready with auth credentials.

¿Alguien puede ayudarme a resolverlo? Estoy buscando en Google desde hace una semana con respecto a esto, pero no obtuve nada útil. Mi código escrito en Appdelegate.m es

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Register for remote notifications
    if (floor(NSFoundationVersionNumber) <= NSFoundationVersionNumber_iOS_7_1) {
        // iOS 7.1 or earlier
        UIRemoteNotificationType allNotificationTypes =
        (UIRemoteNotificationTypeSound | UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeBadge);
        [application registerForRemoteNotificationTypes:allNotificationTypes];
    } else {
        // iOS 8 or later
        // [END_EXCLUDE]
        UIUserNotificationType allNotificationTypes =
        (UIUserNotificationTypeSound | UIUserNotificationTypeAlert | UIUserNotificationTypeBadge);
        UIUserNotificationSettings *settings =
        [UIUserNotificationSettings settingsForTypes:allNotificationTypes categories:nil];
        [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
        [[UIApplication sharedApplication] registerForRemoteNotifications];
    }

    // [START configure_firebase]
    [FIRApp configure];
    // [END configure_firebase]

    // Add observer for InstanceID token refresh callback.
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(tokenRefreshNotification:)
                                                 name:kFIRInstanceIDTokenRefreshNotification object:nil];
    return YES;
}

// [START receive_message]
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
    // If you are receiving a notification message while your app is in the background,
    // this callback will not be fired till the user taps on the notification launching the application.
    // TODO: Handle data of notification

    // Print message ID.
    NSLog(@"Message ID: %@", userInfo[@"gcm.message_id"]);

    // Pring full message.
    NSLog(@"%@", userInfo);
}
// [END receive_message]

// [START refresh_token]
- (void)tokenRefreshNotification:(NSNotification *)notification {
    // Note that this callback will be fired everytime a new token is generated, including the first
    // time. So if you need to retrieve the token as soon as it is available this is where that
    // should be done.
    NSString *refreshedToken = [[FIRInstanceID instanceID] token];
    NSLog(@"InstanceID token: %@", refreshedToken);

    // Connect to FCM since connection may have failed when attempted before having a token.
    [self connectToFcm];

    // TODO: If necessary send token to appliation server.
}
// [END refresh_token]

// [START connect_to_fcm]
- (void)connectToFcm {
    [[FIRMessaging messaging] connectWithCompletion:^(NSError * _Nullable error) {
        if (error != nil) {
            NSLog(@"Unable to connect to FCM. %@", error);
        } else {
            NSLog(@"Connected to FCM.");
        }
    }];
}
// [END connect_to_fcm]

- (void)applicationDidBecomeActive:(UIApplication *)application {
    [self connectToFcm];
}

// [START disconnect_from_fcm]
- (void)applicationDidEnterBackground:(UIApplication *)application {
    [[FIRMessaging messaging] disconnect];
    NSLog(@"Disconnected from FCM");
}
// [END disconnect_from_fcm]

Espero recibir una respuesta pronto. ¡Gracias por adelantado!