I came across a great problem when migrating Lync 2010 to Lync 2013 recently. This issue did not manifest itself with pilot users on 2013 but it was immediately noticed following the bulk migration of all users, and services to 2013.
The migration was successful and everything was working except conferencing. When a user tried to join the conference from a Lync client, it appeared to be ok initially but the audio would not connect. I got a very non-descript “Conferencing error” message. Additionally, I could not share polls, whiteboards etc. Users who tried to join using dial-in conferencing were prompted for a conference ID but upon entering a valid ID, they were told that a conference with that ID could not be found.
It turned out that this was caused by the presence of a legacy Conferencing Directory which had been around since OCS. I ran the following command to determine that a legacy conferencing directory existed:
This lists all of the conference directories that are available and provides an ID number attribute for each. The presence of a conference directory which has a service ID including “BackCompatSite” means that you have a legacy (OCS) conferencing directory. To resolve the problem, I deleted this conference directory, restarted the services and conferencing was available. To delete the conferencing directory I used:
Remove-CsConferenceDirectory –identity -force
Caution! Make sure you identify the legacy conference directory correctly with the right ID number. If you delete a live conference directory, users will need to reschedule all future dated conferences.