Can't make Enterprise Voice calls when Lync 2013 (Skype for Business) connects to the external network

Symptoms

When this issue occurs, users that are connected remotely can't make Enterprise Voice calls in Microsoft Lync 2013 (Skype for Business).

To fix this issue, install the July 5, 2016, update (KB3115261) for Lync 2013 (Skype for Business).

Note Lync 2013 was upgraded to Skype for Business in April 2015.