modal pop up post back problem

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ASP.NET

i have a modal pop up in my web form. i have two buttons .when i click the find button the modal pop up opens up and the is proceeded after that i close the pop up and save the records . the next time i click the find button the pop up is not opening

Here is the code

<asp:UpdatePanel ID="Up" runat="server">
    
    
    <asp:Button ID="btnDummy" runat="server" Text="" BackColor="White" Height="0px" Width="0px" />

        <asp:Button ID="btnclose" runat="server" BackColor="White" Height="0px" Text="" 
            Width="0px" />

 <cc1:ModalPopupExtender ID="btnclose_ModalPopupExtender" BackgroundCssClass="modalBackground"
              runat="server"  OkControlID="btnOkay" CancelControlID="btnclose" TargetControlID="btnDummy"
            PopupControlID="pnlYesNo" Drag="true" 
            PopupDragHandleControlID="PopupHeader">
        
        <cc1:ModalPopupExtender ID="ModalPopupExtender1"   runat="server" 
            BackgroundCssClass="modalBackground" CancelControlID="btnCancel" Drag="true" 
            OkControlID="btnOkay" PopupControlID="pnlYesNo" 
            PopupDragHandleControlID="PopupHeader" TargetControlID="btnDummy">
        
        <asp:Panel ID="pnlYesNo" runat="server" class="popupConfirmation" >
           <div class="popup_Container">
                <div class="popup_Titlebar" id="PopupHeader">
                    <div class="TitlebarLeft">Popup Header</div>
                    <div class="TitlebarRight"></div>
                </div>
                <div class="popup_Body">
                
                <table width="250" >
                <tr>
                <td align="center" colspan="3" >
                    <asp:Label ID="Label15" runat="server" ForeColor="#3333CC" 
                        Text="Please re-enter the correct FLW ID" Font-Names="Calibri" 
                        Font-Size="Medium">
                    </td>
                <td align="left">
                     </td>
                </tr>
                
                
                    <tr>
                        <td align="right">
                            <asp:Label ID="Label3" runat="server" Font-Names="Calibri" Font-Size="Medium" 
                                ForeColor="#3333CC" Text="FLW ID" Width="80px">
                        </td>
                        <td align="left" width="50">
                            <asp:TextBox ID="txtFLWIDUC" runat="server" MaxLength="10" Width="100px">
                        </td>
                        <td align="left" width="20">
                            <asp:Button ID="btnFindUC" runat="server" BackColor="#1A48C0" Font-Bold="True" 
                                Font-Names="Calibri" Font-Size="Medium" ForeColor="White" Height="24px" 
                                onclick="btnFindUC_Click" Text="Find" Width="80px" />
                        </td>
                        <td align="left">
                             </td>
                    </tr>
                
                
                 <tr>
                  <td colspan="4">
                     <asp:Label ID="Label13" runat="server" Font-Names="Calibri" ForeColor="#3333CC" 
                    Text="This FLW ID is not registered,      Do you want to register the issue?" 
                Font-Bold="True" Visible="False" Font-Size="Large">
                </td>
                </tr>
                 <tr>
                 <td colspan="4" align="center"> 
                 
                 
                     <asp:CheckBox ID="ChkboxYesNo" runat="server" Font-Names="Calibri" 
                         Font-Size="Medium" ForeColor="#3333CC" Text="Register" AutoPostBack="True" 
                         oncheckedchanged="ChkboxYesNo_CheckedChanged" Enabled="False" />
         </td>
        </tr>
        
                    
                    
                   
<tr>
    <td align="center" colspan="4">
   <table>
            <tr>
            <td width="250">
                 </td>

please help me..