roon arc with proxy

I am in China. To smoothly use Roon services, I use Apple TV in conjunction with Stash as a proxy. The gateway and DNS of the Roon Core Server are both pointing to the IP address of the Apple TV. The Roon services, including Qobuz and Tidal, are working fine, but Roon ARC has not been working and gives the following error message: btw port forwarding already configed

{
“ipv4_connectivity”: {“status”:“NetworkError”,“status_code”:504,“error”:“error: Error: ETIMEDOUT, response code: undefined, body: undefined connected? undefined”},
“external_ip”: {“actual_external_ip”:“103.aaa.bbb.ccc”,“actual_external_ipv6”:“null”,“router_external_ip”:“null”},
“natpmp_autoconfig”: {“status”:“NotFound”},
“upnp_autoconfig”: {“status”:“NotFound”}
}