I upgraded to Windows 10 and now my Firewall will not turn on. Anyone have any ideas?

Your Avast installation could be corrupted.
Try a Repair of your installation.
Go to Control Panel/Programs&Features/Avast and click Uninstall/Change
From the Avast Installation options scroll Up/Down and select “Repair”
Make sure to reboot after repair. :slight_smile:

https://www.avast.com/faq.php?article=AVKB204

Have you rebooted your system since installing Windows 10 ???