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