Setting
Visible=false
to the server control in ascx/aspx mark up or in a code behind prevent the control being rendered in DOM. So you will not find them in DOM and it won't be accessible to JavaScript
Better remove Visible="false"
set in the panel and add style display:none
.
If you want to make it in code behind follow this code
pnlUpdateDisplay.Style.Add(HtmlTextWriterStyle.Display,"none");
Then use
$('#<%=pnlUpdateDisplay.ClientID %>').toggle()