In order for the HackerGuardian scan to be successful, your firewall must be set to allow the IP address(es) the scan is coming from.

The IP ranges we use:

CIDR: 64.39.96.0/20 (64.39.96.1 to 64.39.111.254)
CIDR: 139.87.112.0/23 (139.87.112.1 to 139.87.113.254)