Why doesn't ajax modal popup show a datacontrol that is loaded dynamically ?

I am using Ajax popup extender which should show gridview upon clicking a imagebutton in inside another gridview but POPUP doesn't show any datacontrol that is populated dynamically even a label. 

Why ? 

<asp:UpdatePanel ID="updMdl" runat="server" UpdateMode="Conditional"><ContentTemplate><asp:HiddenField ID="lnkFake" runat="server" /><asp:ModalPopupExtender runat="server" BackgroundCssClass="modal" ID="mdlPopUpShowHearingsData" TargetControlID="lnkfake"
PopupControlID="popUp"></asp:ModalPopupExtender><asp:Panel runat="server" ID="popUp" CssClass="modalPopup"><asp:Label runat="server" ID="lbl" ClientIDMode="Static" CssClass="label-blue" Font-Size="Larger"></asp:Label><h2>hihihiiuhhuihhuuiiuhhiu</h2><asp:GridView runat="server" ID="grdviewCaseHearingsDetails" ClientIDMode="Static" AllowPaging="true"
PageSize="15" OnPageIndexChanging="grdviewCaseHearingsDetails_PageIndexChanging"
PagerStyle-BackColor="#99CC99" HeaderStyle-BackColor="#99CC99"
DataKeyNames="pk_CaseHearings_ID" AutoGenerateColumns="false"
CssClass="table table-condensed table-bordered table-striped table-responsive scrollable" Width="110%" Style="margin: -6px 9px -5px -21px"></asp:GridView></asp:Panel></ContentTemplate></asp:UpdatePanel>

protected void grdViewCasesByCaseNo_RowCommand(object sender, GridViewCommandEventArgs e)
{

int index = Convert.ToInt32(e.CommandArgument);
int CaseID = Convert.ToInt32(grdViewCasesByCaseNo.DataKeys[index].Value);

if (e.CommandName == "cmdHearingDetails")
{

updMdl.Update();
mdlPopUpShowHearingsData.Show();
lbl.Text= "Show me something";
popUp.Visible = true;





}
}