Merge pull request #3190 from MicrosoftDocs/paulliew-patch-1

Update use-single-tenant-server-server-authentication.md

Author: KumarVivek

powerapps-docs/developer/common-data-service/use-single-tenant-server-server-authentication.md

@@ -97,6 +97,9 @@ To create an unlicensed "application user" in your environment, follow these ste
 
 7. Before exiting the user form, choose **MANAGE ROLES** and assign a security role to this application user so that the application user can access the desired organization data.
 
+> [!NOTE]
+> In an environment, only one Application User for each Azure AD registered application is supported.
+
 > [!IMPORTANT]
 > When developing a real-world application using S2S, you should use a custom security role which can be stored in a solution and distributed along with your application.