Consider the following scenario:
You deploy at least 3 front-end servers in a Microsoft Lync Server 2013 Enterprise Edition pool.
You configure dial-in conferencing in the Lync Server 2013 environment.
You apply the January 2014 cumulative update for Lync Server 2013.
A public switched telephone network (PSTN) user tries to dial in to a Lync conference that is created in the environment.
In this scenario, the user cannot join the conference and receives the following error message:
Sorry, I can't find the meeting with that number
This issue occurs because the PSTN Conference ID mapping is orphaned in your SQL database. Therefore, Lync Server 2013 cannot find the Conference ID.
To prevent this issue from reoccurring, install the following cumulative update:
2937310 August 2014 Cumulative Update 5.0.8308.738 for Lync Server 2013 (Front End Server and Edge Server)
Note If you encounter this issue before you install this update, contact Microsoft Customer Support Services.