If you installed using the 180-day Evaluation ISO and later purchased a license, do not reinstall. Use DISM (Deployment Imaging and Servicing Management) to convert:
Unlike previous versions, Windows Server 2016 transitioned from licensing by processor sockets to licensing by . microsoft windows server 2016 iso
Typically available in Standard and Datacenter editions. If you installed using the 180-day Evaluation ISO
You are trying to use a product key (like an MAK or KMS client key) during installation from an evaluation ISO. Fix: Use a VLSC ISO or skip key entry during installation (choose "I don't have a product key"). microsoft windows server 2016 iso
For immediate, actionable information, you can evaluate Windows Server 2016 directly from the Microsoft Evaluation Center.