Ubiquiti UniFi Cloud Gateway Ultra port forwarding is not working

The checks in more detail

Set the device to a fixed address first, either by setting a static address on it or by making a DHCP reservation in the application, since a changed address breaks the rule. If it does not work, check the basics. The gateway's WAN address must be public: if your provider uses carrier-grade NAT, the address shown for the gateway begins with 100.64 to 100.127, or is a private address, and forwarding from the internet cannot work until the provider gives you a public address. Test from outside your network, such as from a phone on mobile data, because testing from inside often fails without hairpin NAT. Make sure the device's own firewall allows the connection and that the service is listening on the port.

Check that no other rule or Intrusion Prevention feature is blocking the traffic. Security matters. Forward only the ports you need, prefer a VPN to opening a service to the whole internet and keep the service up to date. Check the gateway's logs for blocked traffic. If you change the gateway's WAN type or restart it, the rules persist. For cameras and game servers, use the vendor's recommended ports. Some devices can use UPnP, which Ubiquiti lets you enable, but manual rules are easier to control. Contact Ubiquiti support if a correct rule on a public address does not work, and send a support file.

In UniFi, forwarding is separate from the firewall: a rule in Port Forwarding makes the translation, but a firewall policy in the Zone-Based Firewall or the older Traffic Rules can still block the traffic, so check the Security settings for a rule that drops traffic from the internet to the internal zone. If you have a Dream Machine or another router in front of the gateway, there are two layers of translation and you must forward on both. Dynamic DNS can provide a name for a home address that changes. Keep the forwarded device updated and avoid forwarding administrative services such as remote desktop.