If you receive an error message following:

“The product key you entered didn’t work. Check the product key and try again, or enter a different one". You're running an Evaluation, must be converted to full/retail version before activation.

• If your server already installed an Evaluation version, must be converted to full/retail version before activate, please follow instructions below:
• Run command prompt or PowerShell as administrator:

Type following command: dism /online /set-edition:ServerDatacenter /productkey:xxxxx-xxxxx-xxxxx-xxxxx-xxxxx /accepteula . (Replace xxxx with your activation key).