Take a look to the following document:
http://www.cisco.com/en/US/products/sw/voicesw/ps2237/prod_troubleshooting_guide_chapter09186a0080449da1.html
-Please restart the AvNotifierMgr and AvMsgStoreMonitorSvr services in the Unity server.
-In your Unity server, please go to start > programs > Unity > Manage Integrations > expand the "Cisco Unity Server" > select the callmanager server to which your Unity server is integrated > expand the selected callmanager server > click on "properties" > select the "integration" tab > go to "MWI Synchronization"> click on the "Resynchronize Now" button. If that does not help, we will need to do more troubleshooting. With MWI issues, there are three main sections to check:
1) Between Call Manager and the IP Phone.
To test this, from the phone itself, manually dial the MWI ON and MWI OFF codes. If the lamp correctly changes state, then this leg is working correctly.
Is the MWI lamp correctly changes state when you manually dial the MWI on and MWI off codes?
Make sure the calling search space that is used by subscriber phones contains the partition that contains the route pattern/hunt pilot (voice mail pilot number). If the partition that contains the voice mail pilot number is not in the calling search space that is used by subscriber phones, the phones will not be able to dial the Cisco Unity server.
Confirm that the voice mail ports and phones are in the same calling search space. This calling search space must allows calls to the subscriber phones and any required network devices. This calling search space must include partitions that contain all devices Cisco Unity needs to access (for example, during call transfers, message notifications, and MWI activations).
2) Between Unity and Exchange.
Go to the Unity Admin page > subscribers > subscribers > find/select a subscriber > messages > make note of the status of the "Indicator Lamps" parameter (what is the status?) > click on the "refresh status" button and see if it changes (what is the status now?)
At the desktop of this Unity server, double click on "Unity tools depot" > expand the "switch integration tools" folder > double click on "port status monitor". It will show you the use of your voice ports in real time.
Call the Unity subscriber and leave a message for him. Check the port status monitor. Is Unity calling the MWI extension?
Now go again to the subscriber?s page in Unity admin, go to messages and verify again the status of the "Indicator Lamps" parameter (what is the status?) > click on the "refresh status" button and see if it changes (what is the status now?)
3) Between Unity and Call Manager.
-This section is harder to test. Start by going to the Port Status Monitor (Unity Tools Depot > Switch Integration Tools) and check what state the ports are in. If they show that they're in use, and have been for quite some time, then some of the ports are locking up.
-We should check that the TSP is configured correctly (start > programs > Unity > Manage Integrations > Cisco CallManager cluster) and that the voice ports prefix matches between Call Manager and Unity.
-We can manually call each Unity port from an IP Phone, to make sure that the ports are registering right.
-Finally, we can check that Unity is configured to send MWI on any of the voice ports: start > programs > Unity > Manage Integrations > Cisco CallManager cluster > select the "ports" tab > verify the column "dialout MWI".
