https://support.microsoft.com/en-au/topic/attendees-can-t-see-a-shared-desktop-when-they-join-an-online-meeting-in-lync-2013-19cc4db0-0d15-cc89-2512-31aac7092e0e
Fixes an issue that prevents external users who aren't federated the organizer's company from seeing the shared content or another attendee's desktop in Lync...
shared desktopattendeesseejoin