Hello,
That's the answer of Avast support:
"Dear....................,
Thank you for your response.
My name is .................. and I will asssist you in absence of my collegue.
Your have bought your subscription on a reseller website, so this subscription is not related to your e-mail address in our system, and therefor it will never be visible on your Avast account. Only subscriptions bought on our official website are available on Avast account.
Unfortunately there is nothing we can do to change this.
I stay at your disposal for any other help.
Kind regards,
...................
Avast Customer Care"