You just need to re-issue the license. Please be aware that you can do this at any time you need to from the WHMCS client area without needing to contact support. Simply login @ http://www.whmcs.com/members/clientarea.php click the My Licences & Services link on the right menu, then the green arrow next to your license, and the re-issue button can be found on that license info page. Then the next time you visit your WHMCS installation, the domain and IP address you access it on will be recorded and these will become the new valid license details held by the WHMCS licensing system.