Notification does not always fires

Dear Gurus!

I use VS 2012 and silverlight project in c#. I am trying to make the  event notification system with using signalR.

On the server side I want to use service broker - start notification and when triggered notification - I write the time to static variable. I start notification in Global.asax.cs file as follows:

    public class Global : System.Web.HttpApplication
    {
        const string ConnectionString = @"Server=TERENTIEVAI; Initial Catalog=road; 
             User ID =dependency_client; Password =111111; 
             Trusted_Connection =False; Integrated Security=True; 
             Asynchronous Processing=True; ";

        void Application_Start(object sender, EventArgs e)
        {
            sqlHelper.lastChangesDate = DateTime.Now;
            startWaitingChanges();
        }

        public static void startWaitingChanges()
        {

            SqlDependency.Stop(ConnectionString);
            SqlDependency.Start(ConnectionString);

            using (SqlConnection connection = new SqlConnection(ConnectionString))
            {
                using (SqlCommand cmd = new SqlCommand("Select name,description,date_liquidation from dbo.events", connection))
                {
                    cmd.Notification = null;
                    SqlDependency dependency = new SqlDependency(cmd);
                    dependency.OnChange += new OnChangeEventHandler(HandleChanges);
                    connection.Open();
                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                    }
                    connection.Close();
                }
            }
        }
        public static void HandleChanges(object sender, SqlNotificationEventArgs e)
        {
            sqlHelper.lastChangesDate = DateTime.Now;
            SqlDependency dep = sender as SqlDependency;
            dep.OnChange -= new OnChangeEventHandler(HandleChanges);
    startWaitingChanges();
        }

For the first time  the notification always fires. But then it fires sometimes and sometime it not fires.

What I do wrong?