Try setting the environment variable export PRODIGY_HOST="0.0.0.0" before starting the Prodigy server. This should advertise the server on the WAN IP, instead of the loopback interface (localhost, which is the default). You can also configure the port with the PRODIGY_PORT environment variable.
For production setups, you might want to look into using a reverse proxy in front of the service. I like to use Traefik. Other popular choices include Apache, Nginx and Caddy.