Symptoms
After you move to Microsoft Office 365 Dedicated/ITAR (vNext) from a legacy dedicated environment, some Microsoft Skype for Business 2015 (Microsoft Lync 2013) functionalities don't work.
Resoultion
To fix this issue, install the April 4, 2017, update (KB3178731) update for Skype for Business 2015 (Lync 2013).
Note Lync 2013 was upgraded to Skype for Business in April 2015.