Why is it not working in the server?

Question

It works fine in my development pc. When I host to the server, then it shows errors !

CODE:

    private static object AddStockToWebAPI()
    {

        int Status = 0;
        string strMsg = "";

        List<DataAPI> lstd = new List<DataAPI>();
        lstd = GetDataForWebAPI();

        if (lstd.Count > 0)
        {

            string Baseurl = "https://XXXXXXXXXXXXXXXXXXXXX/XXXXXXXXXXXX/stockapi/";

            using (var client = new HttpClient())
            {

                client.BaseAddress = new Uri(Baseurl);
                client.DefaultRequestHeaders.Clear();
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

                HttpResponseMessage Res = client.PostAsJsonAsync("stockupdateapi", lstd).Result;
                if (Res.IsSuccessStatusCode)
                {
                    var Response = Res.Content.ReadAsStringAsync().Result;
                    JObject brandJOBject = JObject.Parse(Response);

                    Status = Convert.ToInt32(brandJOBject["status"].ToString());
                    strMsg = brandJOBject["message"].ToString();

                }
                else
                {
                    //ERROR: API Unreachable 

                }

                return Status;
            }
        }
        else
        {
            return Status;
        }

    }

ERROR:

HttpResponseMessage Res = client.PostAsJsonAsync("stockupdateapi", lstd).Result;

ERROR DETAIL:

System.AggregateException: One or more errors occurred. ---> System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)
at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)
--- End of inner exception stack trace ---
at System.Net.TlsStream.EndWrite(IAsyncResult asyncResult)
at System.Net.PooledStream.EndWrite(IAsyncResult asyncResult)
at System.Net.ConnectStream.WriteHeadersCallback(IAsyncResult ar)
--- End of inner exception stack trace ---
at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult, TransportContext& context)
at System.Net.Http.HttpClientHandler.GetRequestStreamCallback(IAsyncResult ar)
--- End of inner exception stack trace ---
--- End of inner exception stack trace ---
at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
at System.Threading.Tasks.Task1.GetResultCore(Boolean waitCompletionNotification) at System.Threading.Tasks.Task1.get_Result()
at ONLINESTOCK.Program.AddStockToWebAPI() in D:\WORK\RND\CONSOLEAPP\ONLINESTOCK\ONLINESTOCK\Program.cs:line 87
---> (Inner Exception #0) System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)
at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)
--- End of inner exception stack trace ---
at System.Net.TlsStream.EndWrite(IAsyncResult asyncResult)
at System.Net.PooledStream.EndWrite(IAsyncResult asyncResult)
at System.Net.ConnectStream.WriteHeadersCallback(IAsyncResult ar)
--- End of inner exception stack trace ---
at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult, TransportContext& context)
at System.Net.Http.HttpClientHandler.GetRequestStreamCallback(IAsyncResult ar)
--- End of inner exception stack trace ---<---