This happens due to Cisco Unity's TAPI service provider (TSP) incompatability with the Cisco CallManager version.
Check the versions of Cisco CallManager, Cisco Unity and TSP you are using, and confirm that the three components are compatible.
To determine the current version of TSP, refer to the Determining the Software Version section of Release Notes for Cisco Unity-CM TSP Release 8.0(1).
If you are using an incompatible or older versions of TSP, upgrade to the latest version to resolve the issue. You can download the latest TSP from Software Download-Cisco Unity-CM TSP Software (for registered users).
Note: In Cisco Unity versions earlier than 3.1(1), the Cisco Unity-CM TSP was known as the AV-Cisco TSP.
For upgrade procedures, refer to the Installing the Cisco Unity-CM TSP section of Release Notes for Cisco Unity-CM TSP Release 8.0(1).
To obtain the release notes for all the Cisco Unity-CM TSP versions, refer to Cisco Unity Release notes.
It is not necessary to uninstall an earlier version of the Cisco Unity-CM TSP before installing version 8.0(1). The installation process automatically removes the older Cisco Unity-CM TSP.
If you still need to manually remove the TSP, refer to How to Manually Remove the TSP .
This document applies to Unity 2.x, 3.x and 4.x