Server 2012 Server Core powershell not installed
Use the Deployment Image Servicing and Management (DISM.exe) tool to enable PowerShell:
dism.exe /online /enable-feature /featurename:MicrosoftWindowsPowerShellRoot
...or if that's not enough:
dism.exe /online /enable-feature /featurename:MicrosoftWindowsPowerShell /all
dism.exe /online /enable-feature /featurename:MicrosoftWindowsPowerShellRoot
dism.exe /online /enable-feature /featurename:MicrosoftWindowsPowerShell /all
Say "yes" for reboot.
powershell
Add-WindowsFeature Server-Gui-Shell, Server-Gui-Mgmt-Infra
Shutdown -r -t 0
In server 2012 R2 Use Shutdown /r /t 0