Roon Arc cannot access my Roon Core

Roon Core Machine

ROCK on NUC Barebone BKNUC8V5PNH Core i5-8365U 16GB

Networking Gear & Setup Details

Netgear R6850
NUC connected via ethernet RJ45
All Sonos Devices WIFI

Connected Audio Devices

1 Sonos Port
1 Sonos Move
1 Pair Sonos One
1 Sonos Play 1 Gen 2
All connected via Wifi

Number of Tracks in Library

27000

Description of Issue

I get following error message
{
“connectivity”: {“status”:“NetworkError”,“status_code”:504,“error”:“error: Error: ETIMEDOUT, response code: undefined, body: undefined connected? undefined”},
“external_ip”: {“actual_external_ip”:“84.74.224.117”,“router_external_ip”:“192.168.0.171”},
“status”: “status”: MultipleNatFound
,
“natpmp_autoconfig”: {“status”:“NotFound”},
“upnp_autoconfig”: {“server_ip”:“192.168.1.1”,“found_upnp”:true}
}

Thanks for your support.

Which country are you in and what ISP do you have

Switzerland and ISP is UPC-Cablecom