Error APNS device token not set before retrieving FCM Token for Sender ID

Question

I am receiving messages from firebase for notifications with APNs. In firebase, I have the certificate of APNs key, with the same id in the Xcode project in Firebase that is extracted from Apple Developer.

But I don't know why this could be happening and I get this error and it is registering two tokens in the Messaging extension:

extension AppDelegate : MessagingDelegate {
  func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String?) {}}

APNS device token not set before retrieving FCM Token for Sender ID '########'. Notifications to this FCM Token will not be delivered over APNS.Be sure to re-retrieve the FCM token once the APNS device token is set.

Added what I have in the AppDelegate

import Firebase
import MasivPushIosSdk

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate{

    var firebaseToken: String = ""
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

        FirebaseApp.configure()
        self.registerForFirebaseNotification(application: application)
        Messaging.messaging().delegate = self
        return true
    }
    
    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        Messaging.messaging().apnsToken = deviceToken
    }

    func registerForFirebaseNotification(application: UIApplication) {
        if #available(iOS 10.0, *) {
            // For iOS 10 display notification (sent via APNS)
            UNUserNotificationCenter.current().delegate = self

            let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound]
            UNUserNotificationCenter.current().requestAuthorization(
                options: authOptions,
                completionHandler: {_, _ in })
        } else {
            let settings: UIUserNotificationSettings =
                UIUserNotificationSettings(types: [.alert, .badge, .sound], categories: nil)
            application.registerUserNotificationSettings(settings)
        }

        application.registerForRemoteNotifications()
    }
    
}

extension AppDelegate: MessagingDelegate, UNUserNotificationCenterDelegate {

//MessagingDelegate
    func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String?) {
        self.firebaseToken = fcmToken!
        print("Firebase token: \(fcmToken)")
    }

    //UNUserNotificationCenterDelegate
    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
        print("APNs received with: \(userInfo)")
     }
}

Answer 1

This is a simulator only log. You can safely ignore it. The reason you get this is that Firebase tries to create a mapping from the FCM token to the APNS token so it can send the APNS messages to the iOS devices. However, there is no APNS token on the simulator so the mapping fails.

Try testing it on an actual device to see if you still get the error.