There are situations where users cannot play voice messages to their phone, PC speakers, or may be having issues with authentication. They may see error messages about unable to contact the server, or unknown problems are preventing the completion of the call, etc. There are some client-side registry keys that can be installed and enabled that turn up various Media Master tracing which can aid you/TAC in narrowing down the issue.
How to Enable and Gather Media Master Tracing on the Client Machine for Unity:
"FilesNeededToSetupMediaMasterLogging.zip" is attached to this document which contains the registry files, DBGView tool, and the ReadMe which contains the process below.
Close out all PCA or View Mail for Outlook (VMO) sessions on the client machine to make sure the MediaMaster is not being invoked.
1. Double click the following (this enables the diags):
- trace_mm_on.reg
- trace_RPCAPC_on.reg
- trace_WAVCRYPTO_on.reg
2. Start the DBGView.exe application
- Click Options>Clock Time
- Click Options>Show Milliseconds
3. Start the user's application (VMO, PCA) and reproduce the issue.
4. Gather the diagnostic output from DBGView:
Once you have the output on the DBGView screen, press CTRL-S (File -> Save) to save off the window contents.
5. Close DBGView
6. Double click trace_all_off.reg to turn off the diagnostics on the client machine
How to Enable and Gather Media Master Tracing on the Client Machine for Unity Connection:
View Mail for Notes (VMN) is only offered with Unity Connection. This process also applies for View Mail for Outlook (VMO) being used with Unity Connection.
Step 1 
On the user workstation, on the Outlook Tools menu, click ViewMail for Outlook Options.
Step 2 Click the Diagnostics tab.
Step 3 Enable the following diagnostics:
•Enable VMO Outlook Extension Diagnostics
•Enable VMO Multimedia Diagnostics
Step 4 If the problem is related to secure messages or recording and playback through the phone, enable the following diagnostics:
•Enable VMO Telephone Record/Playback Diagnostics
•Enable VMO HTTP Diagnostics
Step 5 Click OK.
Step 6 Reproduce the problem.
Step 7 Review the resulting log files, which are stored in the C:\Documents and Settings\All Users\Application Data\Cisco Systems\VMO\1.0\Logs folder.
Some Related Defects:
ViewMail, CPCA, SA: Problems with Play/Record over PC speaker/mic
PCA: Cannot select Computer recording on Mac OS X
UC 8.0.2 Quickplay Button in CiscoPCA does not work.