KMS Clients won’t activate and slmgr.vbs -ato fails.
1. Check the KMS activation key is correct
Take a look here for the correct KMS client keys. To change your key use the following command:
slmgr.vbs /ipk product-key-here
Have another go at activating the client with:
2. Check DNS entry for the KMS server
Use NSLOOKUP to confirm the correct DNS record exists for your KMS server, click on the image below for the command:
If the record is wrong or doesn’t exist then follow this TechNet article for instructions on creating the DNS record.
3. Check event log
Look for event ID 12288, it details the attempt to activate.
In this example you can see that despite DNS being correct for our KMS server this client is trying to use itself to activate.
4. Check registry settings
Check under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SoftwareProtectionPlatform, it should look something like this:
KeyManagementServiceName should be the FQDN of your KMS server. If it isn’t we could correct it manually but if DNS is correct then so should this value be. What is more likely is that there is a spurious key with a GUID nested under SoftwareProtectionPlatform and the KeyManagementServiceName value under that key is incorrect. This is likely caused by someone using the KMS server key on this server in error rather than the appropriate client key. Delete the spurious key and try and activate again and it should work fine.