A couple of comments.
After the repair (of Avast), you need to reboot immediately. If you repair and you test the update again without rebooting, it won't work.
Once you reboot, please don't force the update. While having the update settings in "automatic" for engine and definitions updates, let Avast update itself, and only check the result of the update after 10 minutes after the reboot.
Disabling the firewall is not enough. You should delete the firewall rules, reboot and re-create them.
The process that should be allowed by the firewall (if needed, since in many cases it is not even needed) for updates is avast.setup, which needs to include "*" since the exact location may vary from update to update. For Windows Firewall, this is usually not needed, so clean all the Avast related rules and reboot (with no new rules).
You can also check:
Avast main GUI -> Settings -> troubleshooting -> "Load Avast! services only after loading other system services", then save and reboot.
Please report back.