One issue I encountered on W2K12R2, even after installing Putty 64-bit V0.70, was that PowerShell kept saying:
Please install putty (version putty-64bit-0.70) on your machine to use this cmdlet.
I used SysInternal's 'Procmon.exe' utility to monitor PowerShell's access to the registry, and I saw that it was looking for this registry key:
HKCU\SOFTWARE\SimonTatham\PuTTY64
It turned out that my W2K12R2 server didn't have a registry key called 'PuTTY64', it had 'PuTTY'. I added '64' to the registry key, so it looked like 'PuTTY64', and then the InovkeNcSsh cmdlet worked like it was supposed to.
I suspect that I had a 32-bit version of PuTTY installed prior to installing the 64-bit version, and the registry key didn't get updated to 'PuTTY64', since it already existed.
I made sure that the permission were as described elsewhere in a the thread that asulliva linked to:
All application packages: Full Control
Users (of the local machine your on): Full Control
I hope that this information helps others who are trying to get the InovkeNcSsh cmdlet to work.