How to show the WaitingPopup control?

<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<syncfusion:GridGroupingControl ID="GridGroupingControl1" ShowWaitingPopupOnPostBack="true" runat="server" AjaxAutoformat="Midnight" EnableCallbacks="false" ShowGroupDropArea="false" EnableAjaxMode="true" EnableAjaxPaging="false">
<TableDescriptor AllowFilter="false"></TableDescriptor><TableOptions AllowSortColumns="false" />
</syncfusion:GridGroupingControl>
<asp:Button ID="action" runat="server" Text="MakePopup" OnClientClick="clickIt();return false;" />
<syncfusion:WaitingPopup DisableOnShowElementID="GridGroupingControl1" ID="WaitingPopup1"
 ClientObjectId="Popup" runat="server" Alignment="MiddleCentre" AutoFormat="Rollers"
  Height="50px" Width="125px" DisabledBackgroundColor="221, 227, 238">
 </syncfusion:WaitingPopup>

        protected void Page_Load(object sender, EventArgs e)
        {
            AppDomain.CurrentDomain.SetData("SQLServerCompactEditionUnderWebHosting", true);
            try
            {
                SqlCeConnection myConnection = new SqlCeConnection(@"Data Source=|DataDirectory|\Northwind.sdf");
                SqlCeDataAdapter myDataAdapter = new SqlCeDataAdapter("SELECT Top (10) [Product ID], [Product Name], [Supplier ID], [Category ID], [Quantity Per Unit], [Unit Price], [Units In Stock], [Units On Order] FROM Products", myConnection);
                DataSet myDataSet = new DataSet();
                myDataAdapter.Fill(myDataSet);
                DataTable myDataTable = myDataSet.Tables[0];
                this.GridGroupingControl1.DataSource = myDataTable;
            }
            catch (SqlCeException ex)
            {
                throw ex;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

// Popup is a ClientObjectId for the WaitingPopup control- it is used to access the client side API
<script>
 function clickIt()
 {
     if(Popup.IsShown())
         Popup.HidePopup();
     else
         Popup.ShowPopup(); 
  }
</script>