cPanel VPSes are licenses on a per IP basis, the main IP address. If the main IP address changes, then the cPanel license becomes invalid, and has to be reissued. Having said that, sometimes it is necessary to update other values other than the cPanel VPS IP, such as hostname for instance. However, once doing that, you may receive the following error message: "unactivated License". If so, please follow the step-by-step guide on how to resolve this on your cPanel VPS:
Using the above mentioned command, you should now be able to login to your cPanel VPS control panel. However, if you continue to experience any issues, please feel free to reach out to our cPanel VPS support department for further assistance.