This issue occurs when you search for a contact in the search box in Skype for Business when Skype Directory Search is enabled. When this issue occurs, the search times out without any error messages.
Note This issue affects all Middle East countries for which external communications are blocked by an Internet service provider (ISP).
This issue occurs because of the connection to the Transport Layer Security (TLS) session that Skype for Business Edge Server uses to send a client hello. Over this connection, Skype for Business Edge Server never receives a response.
To fix this issue, install the November 10, 2015, security update (KB 3101496) for Lync 2013 (Skype for Business).
Note Lync 2013 was upgraded to Skype for Business in April 2015.