Lync 2013 MCU and Old Conference Directories

After installing a Lync Server 2013 pool and moving users over, you might find they are unable to create new conferences if they are enabled for PSTN dial-in conferencing. When running a SIPStack trace you’ll find the following error during creation of the conference:

Start-Line: SIP/2.0 500 failedLookupForConferenceDirectoryOwner
ms-diagnostics: 3193;reason=”Could not find a front end server that owns the given pstn meetind id.”

Which might lead you to notice that Front-End is logging error Event 51048, LS MCU Factory:

McuFactory could not find the pool associated with one of the conference directories.
Failed to read pool FQDN associated with conference directory 20.

Cause: The pool associated with the conference directory does not exist anymore.
Resolution: Conference directories without a valid pool associated can be deleted using management tools.

The issue seems to be that if orphan conference directories exist, they may prevent new conferences for 2013 users. You can check for orphan directories via: 

Get-CsConferenceDirectory | FT Identity,ServiceID

Review the output and check to see if there is a ServiceID matching a pool which no longer exists. BackCompatSite entries refer to OCS 2007 R2 servers added during a merge operation.

If a Service ID exists for a pool that has been deleted the conference directory cannot be moved at this point, but you can use the following command to forcefully remove it:

Remove-CsConferenceDirectory <Identity Number> –Force

Take care to make sure you’re deleting the correct identity. Removing an active conference directory will force users to reschedule meetings.

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