Android: The push notification badge is not disappearing on my app icon after I open my app again

I use this code in my Android project:

In Activity1.cs:

 public static string MyToken = "";
   static readonly string TAG = "MainActivity";

   internal static readonly string CHANNEL_ID = "my_notification_channel";
   internal static readonly int NOTIFICATION_ID = 100;

 public bool IsPlayServicesAvailable()
 {
     int resultCode = GoogleApiAvailability.Instance.IsGooglePlayServicesAvailable(this);
     if (resultCode != ConnectionResult.Success)
     {
         if (GoogleApiAvailability.Instance.IsUserResolvableError(resultCode))
             Texttest = GoogleApiAvailability.Instance.GetErrorString(resultCode);
         else
         {
             Texttest = "This device is not supported";
             Finish();
         }
         return false;
     }
     else
     {
         Texttest = "Google Play Services is available.";
         return true;
     }
 }

 void CreateNotificationChannel()
 {
     var channel = new NotificationChannel(CHANNEL_ID,
                                   "FCM Notifications",
                                   NotificationImportance.High)
     {

         Description = "Firebase Cloud Messages appear in this channel"
     };
     channel.EnableVibration(true);
     channel.EnableLights(true);
     channel.LightColor = Android.Graphics.Color.Red;
     channel.SetSound(RingtoneManager.GetDefaultUri(RingtoneType.Notification), new AudioAttributes.Builder().SetUsage(AudioUsageKind.Notification).Build());
     channel.LockscreenVisibility = NotificationVisibility.Public;

     var notificationManager = (NotificationManager)GetSystemService(Context.NotificationService);
     notificationManager.CreateNotificationChannel(channel);
 }

 protected override void OnCreate(Bundle bundle)
 {

   IsPlayServicesAvailable();
   CreateNotificationChannel();
   if (Android.OS.Build.VERSION.SdkInt >= BuildVersionCodes.Tiramisu)
   {
       if (!(CheckPermissionGranted(Manifest.Permission.PostNotifications)))
       {
           RequestPostNotificationsPermission();
       }
   }
}


   public bool CheckPermissionGranted(string Permissions)
   {
       // Check if the permission is already available.
       if (ActivityCompat.CheckSelfPermission(this, Permissions) != Permission.Granted)
       {
           return false;
       }
       else
       {
           return true;
       }
   }

   public static int REQUEST_P0STNOTIFICATIONS = 10023;
   string[] reqestPermission = { "android.permission.POST_NOTIFICATIONS" };
   private void RequestPostNotificationsPermission()
   {
       if (ActivityCompat.ShouldShowRequestPermissionRationale(this, "android.permission.POST_NOTIFICATIONS"))
       {
           // Provide an additional rationale to the user if the permission was not granted
           // and the user would benefit from additional context for the use of the permission.
           // For example if the user has previously denied the permission.
           ActivityCompat.RequestPermissions(this, reqestPermission, REQUEST_P0STNOTIFICATIONS);
       }
       else
       {
           //P0STNOTIFICATIONS permission has not been granted yet. Request it directly.
           ActivityCompat.RequestPermissions(this, reqestPermission, REQUEST_P0STNOTIFICATIONS);      
       }    
   } 

using System;
using Android.App;
using Android.Content;
using Android.Util;
using Firebase.Messaging;
using System.Collections.Generic;
using AndroidX.Preference;
using Android.Media;
using AndroidX.Core.App;
using AndroidX.Core.Content;
using Android.Graphics;

namespace MyProjectAndroid
{
    [Service]
    [IntentFilter(new[] { "com.google.firebase.MESSAGING_EVENT" })]
    public class MyFirebaseMessagingService : FirebaseMessagingService
    {
        const string TAG = "MyFirebaseMsgService";

        public override void OnNewToken(string token)
        {
            Log.Debug(TAG, "Refreshed token: " + token);
            storeToken(token);
        }

        private void storeToken(String token)
        {
            //saving the token on shared preferences
            ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences(Application.Context);
            ISharedPreferencesEditor editor = prefs.Edit();
            editor.PutString("my_token", token);
            editor.Apply();   // newer APIs
        }

        public override void OnMessageReceived(RemoteMessage message)
        {
            Log.Debug(TAG, "From: " + message.From);
            var body = message.GetNotification().Body;
            var title = message.GetNotification().Title;
            var sound = message.GetNotification().Sound;
            var colortest = message.GetNotification().Color;
            Log.Debug(TAG, "Notification Message Body: " + message.GetNotification().Body);
            SendNotification(body, title, sound, colortest, message.Data);
        }

        void SendNotification(string messageBody, string Title, string messageSound, string messageColor, IDictionary<string, string> data)
        {
            var intent = new Intent(this, typeof(Activity1));
            intent.AddFlags(ActivityFlags.ClearTop);
            foreach (var key in data.Keys)
            {
                intent.PutExtra(key, data[key]);
            }

            var pendingIntent = PendingIntent.GetActivity(this, Activity1.NOTIFICATION_ID, intent, PendingIntentFlags.Immutable);

                     int color = Color.Argb(255, 76, 178, 252);
            var notificationBuilder = new NotificationCompat.Builder(this, Activity1.CHANNEL_ID)
                                      .SetSmallIcon(Resource.Drawable.ic_stat_name1)
                                      .SetColor(color)
                                      .SetContentTitle(Title)
                                      .SetContentText(messageBody)
                                      .SetSound(RingtoneManager.GetDefaultUri(RingtoneType.Notification))
                                      .SetVibrate(new long[] { 1000, 1000, 0, 0, 0 })
                                      .SetLights(Android.Graphics.Color.Red, 3000, 3000)
                                      .SetPriority((int)NotificationPriority.High)
                                      .SetAutoCancel(true)
                                      .SetContentIntent(pendingIntent);

            var notificationManager = NotificationManagerCompat.From(this);
            notificationManager.Notify(Activity1.NOTIFICATION_ID, notificationBuilder.Build());
        }
    }
}

using System;
namespace SharedCode
{
#if __IOS__
    public partial class PushNotificationService
    {
        public partial void PushLocalNotification();//Define the cross-platform API, which includes a partial method named PushLocalNotification.
        public partial void CheckNotificationPermission(Action action);
    }
#endif
}