The ConfCheckMcuAvailability stored procedure times out. Additionally, you receive Lync Event ID 32050 that resembles the following in the Pool Member logs:
This issue occurs because of a deadlock in the ConfSetMcu stored procedure. When this deadlock occurs, Focus continuously sends an AddConference request to the unallocated multipoint control unit (MCU) in the front-end pool. However, the MCU rejects the request based on its current state.
Article ID: 3070721 - Last Review: Jul 10, 2015 - Revision: 1
Microsoft Lync Server 2013