Do you have generic exception handler in your Global.asax?

Add your code to handle generic exception of your ASP.NET application in Application_Error.

private static readonly ILog log = LogManager.GetLogger(typeof(MvcApplication));

protected void Application_Error(object sender, EventArgs e)
{
    Exception ex = Server.GetLastError().GetBaseException();
    log.Fatal("Unhandled Exception", ex);
}

Figure. Exception handler in Global.asax.cs