Assume that you send a video as an attendee in a conference in Microsoft Skype for Business using Citrix RealTime Optimization Pack 2.0. In this situation, the video button on your client is in pause state although the video can be viewed by the other users in the conference. This issue occurs when the conference presenter first selects the No Attendee Video option by selecting the Invite More People icon > Actions > No Attendee Video, and then selects the Allow Attendee Video option.
To fix this issue, install the February 9, 2016 update (KB3114732) for Lync 2013 (Skype for Business).
Note Lync 2013 was upgraded to Skype for Business in April 2015. And Citrix RealTime Optimization Pack 2.0 requires the Skype for Business client.