The Lync client would not load the Powerpoint presentation before the Office Web Apps Update
After the update has been installed on the Office Web Apps server it works like a charm.
Screenshot with Windows version
Description of the Office Web Apps Server 2013 update 2837634: November 12, 2013
http://support.microsoft.com/kb/2837634/en-us
This update provides the latest fixes for Office Web Apps Server 2013. It also includes stability and performance improvements.
Note: It does not really say too much but it does fix the issue for Lync Powerpoint Sharing on Windows 8.1
Important: Don't forget to update according to this Microsoft article
Apply software updates to Office Web Apps Server
http://technet.microsoft.com/en-us/library/jj966220.aspx