I just downloaded the newest version of Avast this morning, and I thought my firewall wasn't working. Nothing was showing up in the firewall log. I even disabled my router firewall, thinking it might be blocking traffic to Avast.
I found that when Avast is installed the firewall log is disabled. I had to turn it on. Avast is now logging blocked inbound, and outbound traffic, with my router firewall, and Windows firewall turned. They all work together just fine.
I turned it on here: