Thank you for your wellcome

By reading most of the posts concerning the registrations, I found "the" solution...
Someone or something changed the date of my PC to sep. 2020....
By resetting to the correct date and re-installing avast, I was able to register again and to upgrade..... I'm happy..... LOL, who made that joke...
Thank to everyone on that forum who gave me the right answers.
NOTA : I think something is wrong in the registration when the PC date is wrong. The error message could be modified to warn if the date could be wrong.