Hi and welcome to Arturia forums.
Perhaps Arturia support can help you. But this problem might be for Guitar Website to solve.
If the controller have been in the hand of another customer, as i read you suspect, then the license might be registred allready. That would mean, that someone else allready have access to the software, that come with the controller. That need to be unregistred, as someone else otherwise will have the software for free.
It's Guitar Websites responsibility to give you a product, that's not damaged, and that can be registred. Return the product to get a new unit and the software that come with it.
Perhaps Arturia support contact Guitar Website, or can fix this issue somehow. Afterall theReturn the product to get a new unit, can be Arturias responsibility, if in example the product has'nt been registred before or the registration preocess does'nt work correct. But if the site show you can unlock the product, then it might be refistred allready. I can't tell.
Good luck