Symptoms
Assume that you join a large conference as a participant in Microsoft Skype for Business 2015 (Microsoft Lync 2013). When a user shares a video, you may only see a blue picture.
Resolution
To fix this issue, install the April 4, 2017, update (KB3178731) for Skype for Business 2015 (Lync 2013).
Note Lync 2013 was upgraded to Skype for Business in April 2015.