Cannot connect Roon arc to Roon core vía airport express

This is what Roon write{
“connectivity”: {“status”:“NetworkError”,“status_code”:504,“error”:“error: Error: ETIMEDOUT, response code: undefined, body: undefined connected? undefined”},
“external_ip”: {“actual_external_ip”:“”,“router_external_ip”:null},
“natpmp_autoconfig”: {“server_ip”:“”,“found_natpmp”:true},
“upnp_autoconfig”: {“status”:“NotFound”}
I ve already check the airport has the Nat option and I’ve already disconnect the firewall and still not working

I manually inserted the IP address for Roon core and the port number on my airport extreme (port settings) , then it auto connected.

Hi… Thanks a lot but I know nothing a out computers. Could you explain me how to do it if it is not too much trouble?

Refer to Roon ARC and Apple AirPort Extreme router - #4 by Dennis_Bartelheim for a good example.