Tunnelblick is designed to control server processes that it created and/or client processes that it created. It is not designed to control OpenVPN processes that have been created or started by something else, including, for example, OpenVPN Access Server.
Tunnelblick doesn't do much with OpenVPN server processes – it starts and stops them, but it doesn't do much more than that. For example, it doesn't list active sessions, have the ability to terminate active sessions, etc. Doesn't OpenVPN Access Server do that?