Symptoms
If you have a Survivable Branch Appliance policy assigned, you cannot escalate a VoIP or PSTN conversation call to a conference call if location-based routing is enforced in Microsoft Skype for Business Server 2015.
Resolution
To fix this issue, install the August 2021 cumulative update 6.0.9319.619 for Skype for Business Server 2015, Front End Server and Edge Server.
