The video calling with Lync requires Skype for Windows desktop client version 7.0.x.100. We are experiencing issues with some browser versions where an older client is downloaded. If you’ve downloaded at the link below, and the version is not 7.0.x.100, please download using a different browser.
In 2013, we enabled Lync users to contact people on Skype using instant messaging, presence, and audio calling right from your contact list. I’m happy to say that we’ve now taken the next step by adding video calling between Lync 2013 and the latest Skype for Windows desktop client, available for download here. Now Lync users can conduct everyday business and collaboration “face-to-face” with customers, partners and suppliers who use Skype.
Read more at source: http://blogs.office.com/2014/12/05/video-calling-skype-lync-available-now/