In my case I'm testing fcm token to firebase with when user sign ins I'm trying to get token to save it on my firestore. So here is my AuthManager func configureAuthStateChanges() { authStateHandle = auth.addStateDidChangeListener { auth, user in if (user != nil) { self.isSigned = true Messaging.messaging().token(){token,error in if let fcmToken = token{ FirestorageManager.shared.saveTokenToFirestore(token: fcmToken) } if let error = error{ print("error ->", error.localizedDescription) } } }else { self.isSigned = false } print("Auth changed: \(user != nil)") self.updateState(user: user) } } When user sign in then I get this error: error -> İşlem tamamlanamadı. No APNS token specified before fetching FCM Token So my solution was in my CustomAppDelegate I add this function and I test it even with empty body I was able to save it on firestore when user sign in Here is function which I added on CustomAppDelegate: func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) { }