If you get an activation error with server and your version says evaluation like this screenshot.



 


Use this command and replace XXXXX-XXXXX-XXXXX-XXXXX-XXXXX with your product key please note this will upgrade your server from Evaluation to the full license this can take 15-30 minutes so expect some downtime of your server.


Server Standard


DISM /online /Set-Edition:ServerStandard /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX /AcceptEULA


 


Server Datacenter


DISM /online /Set-Edition:ServerDatacenter /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX /AcceptEULA