development certificate : The message received was unexpected or badly formatted

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Apple

iOS

i'm using apns notifications to send push notification to ios devices, when i use a production certificate everything works fine, but when i use a development certificate i keep getting : A call to SSPI failed, see inner exception : The message received was unexpected or badly formatted although i'm changing the sandbox to true

any advice ?

below is my code :

public bool PushMessage(string testDeviceToken, string message, NotificationService service, int i, string szHiddenMessage,string tag)
    {
        var payload1 =new NotificationPayload();
        try
        {
            payload1 = new NotificationPayload(message, 1, "Default");
            payload1.AddCustom("message", szHiddenMessage);
            var push = new Notification(testDeviceToken, payload1);
            alertNotification.Payload.Alert.Body = message;
            if (service.QueueNotification(push))
            {
                UpdateListBox("Notification Queued! " + message);
                return true;
            }
            UpdateListBox("Notification Failed to be Queued!");
            return false;
        }
        catch (Exception ex)
        {
            Global.WriteToText("PushMessage.", "Exception: {0}" + ex.Message.ToString());
            return false;
        }

    }

this is how i call the above function :

private void SendPushNotifications(DataTable tblToPush)
            {
            string szSandbox = "";
        string szFile  ="";
        string szPassword   ="";
        szSandbox = NGlobal.fnGetConfig("sandbox");
        szFile = NGlobal.fnGetConfig("p12File");
        szPassword = NGlobal.fnGetConfig("p12FilePassword");
        bool sandbox = false; //prod
        sandbox = true; //true;
        string p12File = szFile;
        string p12FilePassword = szPassword;
        string p12Filename = System.IO.Path.Combine(AppDomain.CurrentDomain.BaseDirectory, p12File);
        NotificationService service = new NotificationService(sandbox, p12Filename, p12FilePassword,1);
        service.SendRetries = 5; //5 retries before generating notificationfailed event
        service.ReconnectDelay = 5000; //5 seconds
        service.Error += new NotificationService.OnError(service_Error);
        service.NotificationTooLong += new NotificationService.OnNotificationTooLong(service_NotificationTooLong);
        service.BadDeviceToken += new NotificationService.OnBadDeviceToken(service_BadDeviceToken);
        service.NotificationFailed += new NotificationService.OnNotificationFailed(service_NotificationFailed);
        service.NotificationSuccess += new NotificationService.OnNotificationSuccess(service_NotificationSuccess);
        service.Connecting += new NotificationService.OnConnecting(service_Connecting);
        service.Connected += new NotificationService.OnConnected(service_Connected);
        service.Disconnected += new NotificationService.OnDisconnected(service_Disconnected);
        PushMessage(token, message, service, 1, szHiddenMessage,tag);
        }