Hi,
Do you know, that the product you have purchased is a 10 year old discontinuet product?
The syncrosoft page is/ wasfor a Steinbergs E-Licenser activation system. Even an old one that's discontinuet 10 years ago. Arturia have not used any E-Licenser activation since before V-Collection 4 arrived in 2014. Arturia now use their own Arturia Software Center for activating software. If the product show on your website, then you can try to download Arturia Software Center from here
https://www.arturia.com/support/downloads&manuals, and see if the product show up, and it's possible to activate it that way.
I don't know if you have enough informations. But you can contact Arturia Support, and ask, if you can get a code for the new activation system. If the software have had another owner, then the old owner need to transfere the licenses to you through Arturia.
Even if you can get your product activated, then it's out of date. You will be able to use them, as they are in the latest updates they got, if your can run them in your setup. You have to pay more to get new upgraded versions of the software. The controller you have will still be an old model though.
Seller should have informed you about all this.
I would not buy that old equiptment. I would return it, and get something more up to date. Buing old can be very exspensive. That can buying used products also, if that's the case.
I hope you find a solution.
But i think this is really a seller buyer problem, before it's a Arturia problem, even if Arturia support might be able to help you.