cannot turn on firewall

Avast Business Avast Server Protection
1

Having installed the new version of Avast (20 day trial) I have a message for my attention saying my firewall is not switched on.
However, whatever attempts I make to turn it on just ptompts the message ‘unable to start firewall’.
Any suggestions gratefully received.

2

Repair avast!:

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