I was able to duplicate your problem while trying figure out how to block Google. In the firewall under application rules, I went to Avast Service, packet rules, and changed action from allow to ask.
Avast didn't ask, it just wouldn't let me go to any website. I got the message: Firefox can't find the website. There was no message from Avast, even though Avast was stopping Internet traffic.
I went back an changed the packet rules from ask to allow, I still couldn't go to any website.
I went back to application rules, and Avast Service, where I noticed the icon under allowed connections was dim. I clicked on the fourth from the highest setting, which is friends in and internet out, and the icon brightened up, and everything was fine.
If I knew how to insert an image, I might be able to explain it better.