Hello,
I would like to register offline the free avast antivirus version 17.2.2288 in a PC with Windows Vista, but I don’t find the “Offline Registration” option 
http://C:\Users\dramirezwong\Downloads\AvastRegistration.png
The free version doesn’t require registration anymore.
It no longer requires registration with an email address. It still needs to be registered and,
to do that you need to be on-line.
Hi Diana, not sure if this works with V17, but you could try it.
→ https://www.avast.com/registration-free-antivirus.php
This is to get the registration code offline. After getting the code there is no option to enter the offline registration key in Avast Free Antivirus Subscription Page of AvastUI.
Settings > Subscription > Register now
In the new version of Avast Free Antivirus, it tries to connect to internet only. No other way to key in the code to avastui in offline.
Licensing gets reworked, see: https://forum.avast.com/index.php?topic=198923.0