Popup Not showing

I have my popup set to show up on button Update click but it doesnt show?

Protected Sub btnUpdate_Click(sender As Object, e As System.EventArgs) Handles btnUpdate.Click

        lblText.Text = "Are you sure you want to change your password?"
        mpeCheck.Show()

    End Sub

<asp:ModalPopupExtender ID="mpeCheck" runat="server" PopupControlID="Panel2" TargetControlID="btnNo"
        CancelControlID="btnClose" BackgroundCssClass="modalBackground"></asp:ModalPopupExtender><asp:Panel ID="Panel2" runat="server" CssClass="modalPopup" align="center" Style="display: none"><asp:Label ID="lblText" runat="server" Text=""></asp:Label><br /><br /><br /><asp:Button ID="btnYes" runat="server" Text="Yes" /><asp:Button ID="btnNo" runat="server" Text="No" /></asp:Panel><asp:SqlDataSource ID="SqlUpdate" runat="server" ConnectionString="<%$ ConnectionStrings:FTPConnectionString %>"
        SelectCommand=""></asp:SqlDataSource></asp:Content>