you need to create a file called config.gateway.json under the site name on the controller with these lines.

{
        "service": {
                "nat": {
                        "rule": {
                                "6001": {
                                        "disable": "''"
                                },
                                "6002": {
                                        "disable": "''"
                                },
                                "6003": {
                                        "disable": "''"
                                }
                        }
                }
        }
}

if your are running ubuntu this folder is most likely located under /var/lib/unifi/sites/<site-name> .. if the sites folder exist but not the site itself, log into the controller and create a topology map, this will also create the folder