A system that is using a user's internet connection and router that has a firewall can work, but the firewall can sometimes interfere with communication between the Gateway Node and the internet. If you think that your firewall is preventing communication to and from the Gateway Node then you can add the Gateway Node to the "DMZ" or "Demilitarized Zone". The DMZ is a setting that allows the Gateway Node to be exempt from any firewall rules present on a router. The method of adding the Gateway Node to the DMZ will be different for every make and model of the router and will depend on the manufacturer's specifications. In general, the method of adding a gateway node to a router's DMZ will involve either assigning the Gateway Node a static IP address and using that IP address in the DMZ settings, or using the Gateway Node's MAC address in the DMZ settings.
Configuring the router will need to be done by the end-user or an IT professional hired by the end-user and is not the responsibility of OPIsystems Inc. For information on configuring the firewall and the DMZ on your router, contact the router's manufacturer or consult the router user manual.