Once a license key is registered against a specific system it cannot be used on any other system until it is unregistered on that system.
Should you need to replace or reimage a system that utilises the license key it is important that you first unlock the key so it can be reused.
This can be performed by running the command 'upddutils unregister' in a command / terminal window as described here.
To reuse the key to register the software go to the UPDD menu bar icon, select Register and "Enter a licence key" and paste in the license key.
Uninstalling the software does not unlock the license key. If you have uninstalled you can reinstall the software on the same system as this should pick up the license key from our license server and then you can unregister it. If the system is no longer available please email firstname.lastname@example.org asking for the key to be unlocked and state the key in use.