This issue occurs in a Microsoft Skype for Business Server 2015 environment in one of the following scenarios:
A computer that is running a Microsoft Skype for Business Web App plug-in is connected to network by using a wireless network adapter or a point-to-point protocol (PPP) adapter.
The connection-specific DNS suffix of the wireless network adapter exceeds 31 characters.
Driver-defined description of the wireless network adapter exceeds 63 characters.
Note The audio/video session may be an audio/video call or a conference.
To resolve this issue, install the June 2015 cumulative update 6.0.9319.55 for Skype for Business Server 2015, Skype for Business Web Application.