License Avast free just 20 days

Hi,
I’ve installed latest version of Avast free,but it doesn’t show activation button and states license is valid for 20 days,also after clicking on upgrade,why ? How can I made it of 365 days ? Thanks in advance

Try the following:
https://support.avast.com/en-ww/article/Activate-Free-Antivirus

Note that the “Upgrade” button is only for buying a paid version of Avast.

So, if you have left your bank details (now or in the past), chances are you will be charged for a paid version in 20 days.
the mistake was certainly you click on “upgrade” thinking to activate free avast . That’s not what happened because you activated the trial of the paid version :-[

If this is not your intention, I suggest you contact avast support
https://support.avast.com/en-en/contact/sales?c=true
As said by Dix Huit link , avast free no need to be activated anymore