Why can't I pin the presenting toolbar of "Skype for Business" in a Citrix VDI?

When presenting screen via Skype for Business, the toolbar says "Pied" when i hover the mouse over it. But it seems disabled, below are my details. Kindly help.

Citrix Receiver 4.4.1000.16 VDI details: Windows 7 Professional Service Pack1 Skype for Business 2015