Attach a serial monitor to your node (if it has such an interface), and watch what it says.
If I have such problems, I use Arduino IDE.
I select the MCU board and port to which the node is attached and open the serial monitor.
Usually, it helps to understand what might be the cause of the problem.
The port is open to the web, and according to the logs the gateway successfully joins.
→ On chirpstack’s web interface, the gateways do not turn active…
“Seen” gateways have nothing to do with LoRaWAN devices.
Without any LoRaWAN devices and traffic from LoRaWAN devices, the gateway can still be seen by the server.
You can check the region prefix of the MQTT in the toml file, the prefix needs the be in sync with the LoRaWAN region of the gateway.
For MQTT server, you may need to check if the MQTT client has enough permission (read/wite) to the MQTT topics.