发送通知OneSignal超时

Question

我有一个正常工作的代码。

几天前，此代码开始出现此错误：

Error: c# the operation has timed out 
StackTrace: at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)
   at System.Net.HttpWebRequest.GetRequestStream()
   at NotificationServices.SendMessageOneSignal(String userPlayerId, String message, String templateId) 

我的代码：

public static void SendMessageOneSignal(string userPlayerId, string message, string templateId)
{
    var request = WebRequest.Create("https://onesignal.com/api/v1/notifications") as HttpWebRequest;

    request.KeepAlive = true;
    request.Method = "POST";
    request.ContentType = "application/json; charset=utf-8";

    request.Headers.Add("authorization", ConfigurationManager.AppSettings["OneSignalAuthorization"]);

    var serializer = new JavaScriptSerializer();
    var obj = new
    {
        app_id = ConfigurationManager.AppSettings["OneSignalAPPID"],
        contents = new { en = message },
        include_player_ids = new string[] { userPlayerId },
        template_id = templateId
    };
    var param = serializer.Serialize(obj);
    byte[] byteArray = Encoding.UTF8.GetBytes(param);

    string responseContent = null;

    try
    {
        using (var writer = request.GetRequestStream()) //Exception Error
        {
            writer.Write(byteArray, 0, byteArray.Length);
        }

        using (var response = request.GetResponse() as HttpWebResponse)
        {
            using (var reader = new StreamReader(response.GetResponseStream()))
            {
                responseContent = reader.ReadToEnd();
            }
        }
    }
    catch (WebException ex)
    {
        System.Diagnostics.Debug.WriteLine(ex.Message);
        System.Diagnostics.Debug.WriteLine(new StreamReader(ex.Response.GetResponseStream()).ReadToEnd());
    }

    System.Diagnostics.Debug.WriteLine(responseContent);
}   

OneSignal文档尚可。我可以做些什么来工作？