I have same problem as OP. Unintalled Avast Free (in safe mode), uninstalled Comodo clear all traces of both programs.
Attempt 1. Online installer (Windows firewall turned off, Router firewall disabled) ended with erorr message not installed, conection to avast servers not established (no traffic in task manager jus few peaks with maximum 8 kb/s)
Attempt 2 Online installer (Windows firewall turned on, Router firewall disabled) same results
Attempt 3 Offline installer (Windows firewall turned on, Router firewall disabled) Avast installed, can not update VPS nor program it self via emergency updater. Connection can not be eatablished. One more weird thing. It is not needed to restart my PC after installing Avast in all cases. As observed Avast installer process hangs for quite long time in task manger. Updating VPS always returns unknown erorr.
Note: Log send to support.
Unforunatelly after 5+ years I am back on Win Defender.
Jack