I am unable to offer neither help nor explanation for your experience here.
However I found these two articles for you.
If you used the form referred to in first article then I guess that the reason why you have not received any more communications is because you should just give the 'new owner' the license number of the product in question.
If it is of any help then as far as I have understood then Arturia is French which sometimes may create a slight language barrier. In this case they did what you asked (removed license) and maybe they can not see what else it is that you want them to do.
Honestly I do not really understand either as it kind of sounds as you think that the new owner should get another serial than the one that you have and wants to sell...
How to resell my product / license?
(notice : quote : If you'd like to have your product only unregistered and to manually provide the serial and unlock code to the new owner no need to provide us this email address).
https://support.arturia.com/hc/en-us/articles/4405741338642-How-to-resell-my-product-license-
How to deactivate and reactivate my licenses?
https://support.arturia.com/hc/en-us/articles/4531344889500-How-to-deactivate-and-reactivate-my-licenses-
Thanks for responding and the links. However, Those links don't seem to apply as this license, in my products list, had a button specifically stating I needed to contact support first. So I did.
In return, I was expecting an emailed response back stating they had completed the work and preferably the steps or a link to what the next steps were in the process.
Instead I got no email or notification the work was done. Which left me wondering if it had ever been done or if the ticket was still in queue. Well, until I got tired of waiting and went back a week later to my products page to now see the product gone from my products listing.
And subsequent followups to confirm the serial and unlock code (which I provided in the ticket) have gone without a response back as well.
So really I'm looking for a response back from support or to find a communication avenue that allows for two way dialog (if my email provider is silently blocking). That doesn't seem unrealistic to me. Every other support communication has had one. Both in past experiences I've had with Arturia and with other companies.