Based on the error message you provided, it appears that Roon is unable to open the necessary port using UPnP. We recommend manually configuring port forwarding by following the steps in the articles below:
🔗 [url=https://help.roonlabs.com/portal/en/kb/articles/arc-port-forwarding#Overview]ARC: Port Forwarding Overview[/url]
🔗 [url=https://support.google.com/googlenest/answer/6274503?hl=en]Google Nest: Set Up Port Forwarding[/url]
If manual port forwarding does not resolve the issue, we recommend using Tailscale as an alternative solution: