Are you looking to to a newer supported version like Windows Server 2022, or do you need help with a specific error code during activation?
If your server is currently running the , it must be converted to the full Standard version before activation. Use the DISM tool from an elevated command prompt: Open Command Prompt as Administrator. Windows Server 2012 R2 Standard Product Key Activation
Many sites offering free keys or "activation toolkits" package them with malware, Trojans, or backdoors. Revocation: or backdoors. Revocation: