Consider the following scenario in a Microsoft Skype for Business Server 2015 environment:
You have installed the Skype for Business Server 2015 January 2019, March 2019, or May 2019 cumulative update.
You have a third-party contact center, or other application that's based on UCMA. It manages conferences and adjusts Audio/Video Conferencing Server audio routes.
In this situation, you find that randomly you experience conferencing audio/video failures, and you may notice the following event log entry recorded on one or more of your Skype for Business 2015 Front End servers:
Source: LS Audio-Video Conferencing Server
Message: The Audio/Video Conferencing Server has failed to create a conference.
Conference URI: URI;gruu;opaque=app:conf:focus:id:abcdefgh Exception: Media Processor instance is not available to service this request
This issue also occurs in Skype for Business Server 2019.
An issue that's present in the Skype for Business Server 2015 January 2019, March 2019, and May 2019 cumulative updates causes the Audio/Video Conferencing Server to experience a deadlock under certain timing conditions.
To fix this issue, install one of the following updates:
For Skype for Business Server 2019, install the December 2019 cumulative update 7.0.2046.151 for Skype for Business Server 2019, Conferencing Server.
For Skype for Business Server 2015, install the July 2019 cumulative update 6.0.9319.559 for Skype for Business Server 2015, Conferencing Server.
If your Audio/Video Conferencing Server is experiencing this issue, the Audio/Video Conferencing Server service must be restarted to enable it to start to work correctly.
To prevent this issue from reoccurring, roll back to the Skype for Business Server 2015 July 2018 cumulative update on all Front End servers which host conferences that the third-party UCMA applications interact with.