When trying to edit the Windows Firewall policy in the group policy management tool, you get this error:
There was an error opening the Windows Firewall with Advanced Security snap-in
An error occurred while trying to open the policy.
Error: The system cannnot find the path specified
This is because you cannot edit the Windows Firewall group policy from a computer that is not the PDC (Primary Domain Controller). To fix this, log onto the domain controller that is set to be the PDC and edit the Windows Firewall group policy from there instead.