DavidR
2
What Firewall are you using?
With a program update, your firewall may, correctly recognise the avast program has changed and ask you to allow it access, if you didn’t answer YES, that’s it blocked.
Check your firewall allowed/denied access programs/logs, avast.setup needs access to the Internet in order to be able to update.
Try a manual update, and see if your firewall blocks it.