Consider the following scenario:
You connect a Microsoft Lync Phone Edition for Polycom CX600 telephone through a USB connection to a computer that's running a Microsoft Skype for Business client.
You receive an anonymous call on the telephone.
You answer the call as an agent of a response group in Skype for Business.
In this scenario, the conversation window changes to Compact View, and you can't find any call controls to transfer the call.
To fix this issue, install the February 9, 2016 update (KB3114732) for Lync 2013 (Skype for Business).
Note Lync 2013 was upgraded to Skype for Business in April 2015.