First of all, make sure that your AD server is fully configured to accept SSL connection. To verify that your AD server is enabled with LDAPS connection, you can run a Microsoft support tool LDP.EXE on your AD server, enter . Open command prompt and type ldp and press return:
The LDP window will popup:
Enter the server name, and connection port as "636".
Finally, in DualShield, modify the LDAP connection of your Identity Source that's connected to your AD server.