@smilin Jack,
"Something" is not right here. Even in Advanced Mode, Windows Firewall should let you know when it blocks some specific process from connecting (there is even a specific checkbox option to disable the "asking" function of Win FW).
If you set Avast updates to "manual", and wait, say, 13 hours to a manual update, then you could open Windows Task Manager and actually see "avast.setup" when you manually update (using Avast tray icon).
Opening Windows Firewall simultaneously too, should give you the opportunity to revise whether it is blocking something, or the problem is actually something else.
With no real data, there is no way to confirm that Windows Firewall is blocking Avast. IMHO, comparing the "normal mode" of Win FW with the advance mode is not enough. Some additional option or security check "must" be available "somewhere".
Even specialized (firewall) tools can usually work together with Avast, so Windows FW should work too.
Have you tried any of the add-ons controls of Windows Firewall? There are several available.
I know it is a new system, but anyway, have you tried (re)building a "new" network connection setting in Windows?