Free version for three weeks since 10/9. Purchasedd Pro on 10/19; still get same message when attempting to update definitions or program. What gives, Avast?
Since buttoni2 joined your topic, he too recently suffered the "Host unreachable" error and that was down to his firewall blocking the update executable.
In his case the firewall was the win7 one and the executable requiring internet access was the instup.exe is in the avast\setup folder.
What is your firewall (as Avast Free and Avast Pro don't have the Avast Firewall) ?
You could check to see if the instup.exe is in the avast\setup folder is indeed allowed in your firewall.
For more information on other files also see post
https://forum.avast.com/index.php?topic=222896.msg1481589#msg1481589 other posts in that topic may also help.