This can happen if the network configuration interferes with Component Object Model (COM) or Distributed COM (DCOM) operations.
Use this procedure to resolve this issue:
Since the Media Master control bar relies on communication to communicate with the Cisco Unity server, verify that DCOM communication is enabled on the subscriber workstation and on the Cisco Unity server.
Verify that the AvCsMgr and AvCsGateway services run as a distinguished Cisco Unity account (as specified during installation) and not the Local System account.
Apart from this procedure, verify that there is no firewall between the subscriber workstation and the Cisco Unity server. The Media Master control bar does not work through a firewall. Disable virus-scanning services and VPN Client software on the subscriber workstation, as applicable.