firewall will not activate or turn on

as the title states this will not occur for some reason

Repair Avast:

  1. Control Panel → Add/Remove programs → Avast
  2. Click on ‘Repair’.
  3. Follow instructions.
  4. Reboot.

If that doesn’t work and you need to do a clean install of Avast,
the following video may be of help to you:
http://youtu.be/V0P3JFfBCDk