If you are running a Windows Server 2016 standard 180 days evolution copy that you downloaded off Microsoft Website and try to activate the installation with a product key that you purchased for Microsoft Server 2016, you might get an error message saying that it can’t activate, or that you entered a product key that can’t be used to activate Windows with error 0xc004f050, here how you can activate it.
Go to Command Line and type:
Dism /online /Set-Edition:ServerStandard /AcceptEula /ProductKey:xxxxx-xxxxx-xxxxx-xxxx-xxxxx
Where xxxxx-xxxxx-xxxxx-xxxx-xxxxx is the product key you purchased
Process might get stuck at 10% for a little while, give it time. After it is done, you will be asked to reboot. Windows will be all good and permanently activated after it comes back up.