When you perform an application action and receive this kind of error in your action logs:

“Exception occurred in System.Management.Automation: Cannot load Windows PowerShell snap-in Microsoft.PowerShell.Diagnostics because of the following error: Could not load file or assembly ‘Microsoft.PowerShell.Commands’ or one of its dependencies. The system cannot find the file specified”

The most likely cause is not having a new enough version of PowerShell installed.  As of the time of this writing, PeoplePlatform require PowerShell version 3.  We recommend installing the latest version.  As of the time of this writing the latest is version 5.

You can find newer versions of PowerShell in the Windows Management Framework:  https://www.microsoft.com/en-us/download/details.aspx?id=50395 .  After installing, reboot and try your action again, then you should see success.