Push notification is not working when app is in background (minimized) - iOS

I'm newbie to Swift, I am creating chat application, I need to send notification when app is in foreground or minimized.

But I am not getting the notification when app is minimized (it works when USB is connected.

1. Enabled Remote notification

2. Background Fetches in Xcode setup

3. Enabled Push Notification

4. Production APns certificate

Notification code:

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    let gcmMessageIDKey = "gcm.message_id"

    func application(_ application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

        FirebaseApp.configure()

        Messaging.messaging().delegate = self
        Messaging.messaging().shouldEstablishDirectChannel = true

        if #available(iOS 10.0, *) {

            UNUserNotificationCenter.current().delegate = self

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

        application.registerForRemoteNotifications()

        NotificationCenter.default.addObserver(self, selector: #selector(tokenRefreshNotification(_:)), name: NSNotification.Name.InstanceIDTokenRefresh, object: nil)

        return true
    }

    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any]) {

        Messaging.messaging().appDidReceiveMessage(userInfo)         
    }

    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any],
                     fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {

        Messaging.messaging().appDidReceiveMessage(userInfo)

        let action = userInfo["action"] as! String
        let notification = UILocalNotification()
        notification.fireDate = NSDate() as Date
        notification.alertTitle = "test"
        notification.alertBody = "test"
        notification.alertAction = "Ok"
        UIApplication.shared.applicationIconBadgeNumber =  1
        UIApplication.shared.scheduleLocalNotification(notification)

        completionHandler(UIBackgroundFetchResult.newData)
    }

    func application(_ application: UIApplication, didFailToRegisterForRemoteNotificationsWithError error: Error) {
        print("Unable to register for remote notifications: \(error.localizedDescription)")
    }

    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        print("APNs token retrieved: \(deviceToken)")

        // With swizzling disabled you must set the APNs token here.
        Messaging.messaging().apnsToken = deviceToken
    }       
}

@available(iOS 10, *)
extension AppDelegate : UNUserNotificationCenterDelegate {

    func userNotificationCenter(_ center: UNUserNotificationCenter,
                                willPresent notification: UNNotification,
                                withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        let userInfo = notification.request.content.userInfo

        if let messageID = userInfo[gcmMessageIDKey] {
            print("Message ID: \(messageID)")
        }

        completionHandler([.alert, .sound, .badge])
    }

    func userNotificationCenter(_ center: UNUserNotificationCenter,
                                didReceive response: UNNotificationResponse,
                                withCompletionHandler completionHandler: @escaping () -> Void) {
        let userInfo = response.notification.request.content.userInfo

        if let messageID = userInfo[gcmMessageIDKey] {
            print("Message ID: \(messageID)")
        }

        print(userInfo)

        completionHandler()
    }
    @objc func tokenRefreshNotification(_ notification: Notification) {
            guard let token = InstanceID.instanceID().token() else {
            print("No firebase token, aborting registering device")
            return
        }
        print("No firebase token, aborting registering device")           
    }
}   

extension AppDelegate : MessagingDelegate {
    // [START refresh_token]
    func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
        print("Firebase registration token: \(fcmToken)")
        Messaging.messaging().subscribe(toTopic: "/topics/channel_18")           
    }

    func messaging(_ messaging: Messaging, didReceive remoteMessage: MessagingRemoteMessage) {
        print("Received data message: \(remoteMessage.appData)")
    }        
}

FCM Payload:

 {
     "to" : "/topics/channel_18",
     "data" : {
      "action" : "NOTIFY",
      "message" : "{"text":"test" }"
     },
     "content_available" : true
    }

I have tried with Priority high and with Sound option but none works.

Please note that I am not using "notification" key as per client request. i am using only data-message in FCM payload

Please anyone help me to work notification when app is in background without USB connection.