Application_Error not working on production server

Application_Error did not start on production server. but it works on our local server and another amazon server. our local server has a Windows7 version and an IIS version (7.5), but the production server has a Windows8 and IIS version (8+). anyone has any idea.

    void Application_Error(object sender, EventArgs e)
    {
        // Code that runs when an unhandled error occurs
      Exception  ex = Server.GetLastError().GetBaseException();

      string cls = ex.TargetSite.DeclaringType.Name;
      string mtd = ex.TargetSite.Name;

        string ErrorMessage = ex.Message;
        string page = Request.Path;
        string url = Request.PhysicalPath;
        string StackTrace = "";
        string inputdata = "";


        if (ErrorMessage != "File does not exist.")
        {
             StackTrace = ex.StackTrace;
             foreach (string i in Session.Contents)
             {
                 if (Session[i] != null)
                 {
                     if (inputdata != "")
                     {
                         inputdata = inputdata + " , [" + i + "] = " + Session[i].ToString();
                     }
                     else
                     {
                         inputdata = "[" + i + "] = " + Session[i].ToString();
                     }
                 }
             }

            string flg = objBus.insertException(page, "", ErrorMessage, StackTrace, "", url, Session["UserID"].ToString(), inputdata,"");
            //string flg = "0";


            //Response.Redirect("~/ErrorPage.aspx?errorId=" + flg, false);
            Server.Transfer("~/ErrorPage.aspx?errorId=" + flg, false);
        }


    }