The TAPI Service Provider (TSP) ports are not registered.
To resolve the issue, perform this procedure:
Go into the TSP configuration from the console of the server and select Start > Settings > Control Panel > Phone and Modem Options > Advanced > Cisco Unity-CM TSP > Configure.
Ensure that it is set up correctly (with the correct prefix, and so forth).
The Cisco CallManager Device name prefix should be exactly the same as the port names configured for the voice mail ports in Cisco CallManager with the exception of the 1, 2, 3, 4,... appended to each port.
The IP address of the primary server needs to be correct (it is better to use an IP address instead of a name), and the TCP IP port is usually set to the default of port 2000.