Currently, none of the critical complex configuration documentation from the 7.x train visual voicemail document was ported to the new 8.5.1 visual voicemail document for high availability Active Active Unity Connection pair configuration. We are again getting cases in TAC where people follow the current 8.5.1 guide and visual voicemail fails finding a line because their is no complex configuration section for their high availability Active Active configuration.
If people use the current 8.5.1 document to configure visual voicemail on a complex configuration such as a high availability pair, the phones will show inconsistent behavior when using visual voicemail. It will appear to work one time and then other times fail finding an available line. It will show very erratic performance. I have filed a documentation bug CSCtq81646to update the current 8.5.1 visual voicemail documentation with the complex configuration portion of the existing 7.x document.
Current Work Around/Solution:
For now, using the 7.x guide that contains the required configuration missing section fixes the issue. You can find that here....
"Configuring Visual Voicemail on Complex Systems That Involve Failover, Clusters, and Multiple Servers"