Windows Server Manager 2012 – unable to manage role & feature
I have come across this issue a couple of time. It looks like the release of WIndows 2012 R2 this issue has been remediate. This is for all the people that are still running Windows 2012 pre R2.
Open Powershell in admin mode
Run the following command:
dism /online /cleanup-image /restorehealth
Once it is done restart the computer(s).
You should now be able to manage your server again.