To activate Windows Server 2019 via KMS, the client machine must be using a Generic Volume License Key (GVLK). These keys are public and tell the OS to look for a KMS host on the network. Generic Volume License Keys for Windows Server 2019
After installing the GVLK, the system will automatically attempt to discover and activate against a KMS host on the local network. windows server 2019 kms iso link
