6. After activation is complete, restart the Software Licensing Service.
7. Verify that the record is created for the new server in the DNS.
To verify that the KMS host is configured correctly, you can check the KMS count to see if it is increasing. Run slmgr.vbs /dli on the KMS host to obtain the current KMS count. You can also check the Key Management Service log in the Applications and Services Logs folder for 12290 events, which records activation requests from KMS clients. Each event displays the name of the computer and the time-stamp of an individual activation request.
2012 or 2012 R2? You can upgrade from 2012 R2 to 2019 and then add the KMS Host for 2019, you could also install a new server and install KMS (Volume Activation Services) on that and update DNS so that the clients can find the new KMS server using the SRV record