Quickest way to renew cPanel license -
First, you may check if the server has valid license for the server's IP by using cPanel verification link: http://verify.cpanel.net
Thereafter, just enter following command on cPanel server -
root@server [~]# /usr/local/cpanel/cpkeyclt
Output will be as below -
Updating cPanel license...Done. Update succeeded.
Updating cPanel license...Done. Update succeeded.
Building global cache for cpanel...Done
That's all!