The licensing validation is not just a firewall issue. It is a QuickBooks application or executable that also needs access to the Internet. In other words, if you are attempting to completely block QuickBooks from accessing the Internet, but at the same time allow it to validate licensing, you will need to allow the licensing executable to pass through the firewall via an Application Control Manager which could be router based or standalone. It could also be as simple as allowing the executable to pass through the PC firewall running QuickBooks (which should not be blocked by default).