how to fix windows server 'product code did not work' error

If you installed windows server evaluation and our product key is not working, this is because you haven't converted it to full retail version before activation.

If you installed the evaluation version instead of the retail version, you must first convert your installation to retail before activating, by following these steps:

How to convert Windows Server Evaluation to Windows Server Standard / Datacenter full version

4. Once you have installed the evaluation and converted it to the full retail edition, enter the unique activation code that you purchased from us to activate.

5. The CD Key will authenticate with Microsoft automatically, and the activation is complete!  You now own a genuine copy of Windows Server.