Hey mhawas,
are you referencing the report under Reports-->VoIP-->Skype for Business?
If so, then this is more complicated to enable. This required a Connect integration (available with the NMS Advanced License) with the Microsoft Skype API. This API will need to be installed on all your Skype front-end servers and another management package on a dedicated Windows server which centralizes all call stats from all front-ends. That mangement API then forwards the data to Connect (XMC) which then builds that report.
Kurt