how to restrict access to certain aspx page using active directory?

Hello. I already have a code to get the current user login in ad. What i want to happen is that some users will have their access to a certain page but others do not have an access.. how will i do this? I am also done in web.config using the code below: Still, nothing happens in my code. Approver user still access the other page, is there any mistake in my codes or did i miss something? Thanks.
<location path="ApproverPage.aspx">
    <system.web>
      <authorization >
        <allow users="approver"/>
      </authorization>
    </system.web>  
 </location>
 
String LDAPath = ConfigurationSettings.AppSettings["LDAP://ABAKADAEGA.abaka.local/OU=ABAKA Users OU, DC=smart, DC=LOCAL"];

System.Security.Princ ...