Description
On a WHM server, you might get a message such as the following:
The hostname must be a fully qualified domain name (FQDN).
Ensure you have a proper hostname in this format computername.domainname.com
If you have migrated your computer you might also get that message.
To fix the problem, run this WHM utility as root:
/usr/local/cpanel/cpkeyclt
Reference
https://forums.cpanel.net/threads/your-license-could-not-be-activated-because.290681/