Cause
This issue occurs because Microsoft Lync 2013 sets a proxy server but does not set the proxy exception list for the Microsoft Office Online Sign-in Assistant service (MSOIDSVC). Therefore, MSOIDSVC tries to connect an Active Directory Federation Services (ADFS) server through the proxy server. However, the proxy server cannot connect an ADFS server through an external Internet network.
Resolution
To resolve this issue, install the March 10, 2015 update for Lync 2013.
