Asp:Label not displaying on web pages

Hello all:

I have a old asp.net web form application I have been tasked to maintain.  I have a Site.Master page that I've added some server controls on.  This page mainly hold a menu bar with links to various other pages. When someone clicks on a link in a specific section of the menu, they are directed to a sub-folder containing other pages.  These pages are not linked to the master page.

So my issue is on these pages that are not linked, I have an asp:label control that I am trying to populate via ConfigurationManager.AppSettings.  The problem is when the page renders, nothing is showing up, not even the span that would've been created with the asp:label.

The purpose of this control is to display what environment the user is in.  I have it on the Site.Master and it works well, but on the individual page that is not associated with the Site.Master, it does not show up.

on Site.Master:
<asp:Label ID="EnvironmentDescr" runat="server" CssClass="environmentDesc" Text="<%$ AppSettings: EnvironmentDescription %>" />

on individual page:
<asp:Label ID="EnvironmentDescrDO20" runat="server" CssClass="environmentDesc" Text="<%$ AppSettings: EnvironmentDescription %>" />

Can someone please let me know what I am doing wrong?  I have other asp:label controls on the individual page and they're all working.

Many thanks for your assistance!

Juan