I can’t thank you for your patience while we’ve diligently worked to reach every request for support with port forwarding. I know you’ve endured a long wait time, and hopefully we can resolve your issue promptly at this point and restore some faith.
The diagnostics you’ve provided suggest that UPnP is not properly configured on your router.
Please first try the following steps:
Try to toggle UPnP/NATPMP off/on in the web administration interface for the router directly upstream from your Core and then restart the router.
Try to manually open the port in your router’s port forwarding configuration. Then, make sure the IP/Port matches the Port listed in Roon → Settings → ARC. This is the step @Andrew_Griffiths suggested above, so I recommend looking into the content they shared.
Check for any VPNs or Firewalls that might be interfering
If you continue to experience difficulties, please tag the support team and include the following information:
What is the make and model of your modem and router?
Do you have any additional network hardware, like additional routers or managed switches? This is particularly important if you have a second router in your setup.