Can’t join meeting by using Skype for Business Room System or Surface Hub devices in Skype for Business Server 2015

Your end-users report that they can't join a Skype for Business meeting, especially when they join the meeting by using Microsoft Business Room System or Surface Hub devices. 

This issue occurs because all subsequent sign-in processes fail for these devices after a rare race condition occurs in Microsoft Skype for Business Server 2015 Front End service. 

To fix this issue, install the December 2017 cumulative update 6.0.9319.510 for Skype for Business Server 2015, Front End server and Edge server.

To work around this issue, restart the Skype for Business Server 2015 Front End service to have the issue lessened.