ModalPopupExtender did not call with accordion panel

Hi,

I am using Modal Popup Extender in one of my web page. I am using Modal popup extender  to display message in attractive way.  My Web page use accordion panel.  When i press the save button my modal popup extender is not display. If remove Accordion panel then its working fine. 

Here is ASPX

<%@ Page Title="Ny Bokning" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="bk.aspx.cs" Inherits="NewBooking" Culture="sv-SE" %><%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %><asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="Server"><style type="text/css">
        .style1
        {
            width: 100%;
        }</style></asp:Content><asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="Server"><asp:ScriptManager ID="ScriptManager1" runat="server" EnableScriptGlobalization="True"></asp:ScriptManager><center><asp:Panel ID="Panel2" runat="server" Width="95%" CssClass="Panelbg"><center><h3 style="color: #993300;">New Page</h3><asp:Button ID="btnSpara" runat="server" Text="Spara" ValidationGroup="Booking" OnClick="btnSpara_Click"/></center><asp:Label ID="StaticErrorMessage" runat="server" Text="" Visible="false" ForeColor="Red"></asp:Label><br /><asp:Accordion ID="Accordion1" runat="server" SelectedIndex="0" FramesPerSecond="30"
                TransitionDuration="200" FadeTransitions="true" AutoSize="None" HeaderCssClass="accHeading"
                Width="95%"><Panes><asp:AccordionPane ID="BookingHanlder" runat="server"><Header>Övrig info Schema
                        </Header><Content><asp:Label ID="Label1" runat="server" Text="Label"></asp:Label></Content></asp:AccordionPane></Panes></asp:Accordion></asp:Panel><asp:DropShadowExtender ID="Panel2_DropShadowExtender" runat="server" Enabled="True"
            TargetControlID="Panel2" Opacity=".8" Radius="8" Rounded="True"></asp:DropShadowExtender><asp:RoundedCornersExtender ID="Panel2_RoundedCornersExtender" runat="server" Enabled="True"
            TargetControlID="Panel2" Radius="7"></asp:RoundedCornersExtender><!---
Show Message Div
--><div style="min-height: 700px;"><asp:ModalPopupExtender ID="ModalPopupExtender1" BackgroundCssClass="ModalPopupBG"
                runat="server" OkControlID="btnOkay" TargetControlID="lbmsgError" PopupControlID="Panel1"
                Drag="true" PopupDragHandleControlID="PopupHeader"></asp:ModalPopupExtender><div id="Panel1" style="display: none;" class="popupConfirmation"><div class="popup_Container"><div class="popup_Titlebar" id="PopupHeader"><asp:Label ID="lbmsgHeader" runat="server" Text="Error"></asp:Label></div><div class="popup_Body"><p><asp:Label ID="lbmsgError" runat="server" Text=""></asp:Label></p></div><div class="popup_Buttons"><input id="btnOkay" value="Stänga" type="button" /></div></div></div></div></center></asp:Content>

Here is Code Behind

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Collections;
public partial class NewBooking : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (this.Session["UserName"] == null)
        {
            Response.Redirect("~/Account/Login.aspx", true);
        }
        else{
            if (!this.Session["Permission"].ToString().Contains("Booking"))
            {
                Response.Redirect("~/MessageBoard.aspx?Msg=NotPermit&Url=Default.aspx", true);
            }
        }
    }

    //Save Button Click Event
    protected void btnSpara_Click(object sender, EventArgs e) {
        try {
            ShowMessage("Header", "Message");
        }
        catch (Exception exc) {
            ShowMessage("Error Message", exc.Message);
        }
    }

    private void ShowMessage(string MessageHeader, string Message)
    {
        StaticErrorMessage.Text = Message;
        StaticErrorMessage.Visible = true;
        lbmsgHeader.Text = MessageHeader;
        lbmsgError.Text = Message;
        ModalPopupExtender1.Enabled = true;
        ModalPopupExtender1.Show();
    }
}