Silent notification/ Blank Push Notification not updating pass added to Apple Wallet

Question

Hi my project is based on Asp.Net MVC 4.5 and I am having issue while sending blank push notification such that pass added to the user wallet got updated . There's no error in logs and its also working fine while debugging. But when i hard refresh the pass it got updated . It was working but suddenly stopped working recently. I am using following method to send Blank Push / Silent Notification

 public void BlankPushNotificationAPNS(string deviceID, string org_key)
 {
     int port = 2195;
     String hostname = "gateway.push.apple.com";
     DataObject.Configuration config = ConfigurationRepository.Instance.getCofigurationByOrgKey(org_key);
     String certificatePath = HttpContext.Current.Server.MapPath("~/Certificates/") + config.wallet_cert_name;
     //Utility.Logger.LogMsg("Certificate Path : " + certificatePath);
     byte[] certificateBytes = File.ReadAllBytes(certificatePath);
     //using (var webClient = new WebClient())
     //{
     //    certificateBytes = webClient.DownloadData(certificatePath);
     //}
     //Utility.Logger.LogMsg("Certificate Bytes : " + System.Text.Encoding.UTF8.GetString(certificateBytes));
     X509Certificate2 clientCertificate = new X509Certificate2(certificateBytes, config.wallet_cert_password);
     X509Certificate2Collection certificatesCollection = new X509Certificate2Collection(clientCertificate);
     //X509Certificate cert = GetAppleServerCert(thumbprint);
     //Utility.Logger.LogMsg("certificate read");
     TcpClient client = new TcpClient(hostname, port);
     SslStream sslStream = new SslStream(client.GetStream(), false, new RemoteCertificateValidationCallback(ValidateServerCertificate), null);
     //Utility.Logger.LogMsg("certificate read ssl");
     try
     {
         //ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls;
         sslStream.AuthenticateAsClient(hostname, certificatesCollection, SslProtocols.Tls, false);
         MemoryStream memoryStream = new MemoryStream();
         BinaryWriter writer = new BinaryWriter(memoryStream);
         writer.Write((byte)0);
         writer.Write((byte)0);
         writer.Write((byte)32);

         writer.Write(StringToByteArray(deviceID.ToUpper()));
         String payload = "{\"aps\":\"\"}";
         writer.Write((byte)0);
         writer.Write((byte)payload.Length);
         byte[] b1 = System.Text.Encoding.UTF8.GetBytes(payload);
         writer.Write(b1);
         writer.Flush();
         byte[] array = memoryStream.ToArray();
         sslStream.Write(array);
         
         sslStream.Flush();
         client.Close();
     }
     catch (System.Security.Authentication.AuthenticationException ex)
     {
        Utility.Logger.BlankPushLogger("Method:BlankPushNotificationAPNS,AuthenticationException", ex.Message + ", deviceID_" + deviceID + ", org name " + config.org_name_without_spaces);
         client.Close();
     }
     catch (Exception e)
     {
                         Utility.Logger.BlankPushLogger("Method:BlankPushNotificationAPNS,Exception", e.Message + ", deviceID_" + deviceID + ", org name " + config.org_name_without_spaces);
         client.Close();
     }
 }

Is there some changes done by apple in certificates or something else. Since it's working and stopped recently. Any help is appreciated