Hi @David_Page,
Thank you for posting and we’re sorry to hear that you’ve hit a snag with the autoconfiguration of port forwarding for ARC.
I notice you’re using a Vodafone gateway as your modem/router hub. Is Vodafone your service provider? If so, there’s a possibility that UPnP is failing because Vodafone’s CG-NAT is translating the external IPv4 address.
If the steps our moderators provided above don’t help, then I recommend reaching out to Vodafone’s support department to inquire if a dedicated external IP address is available for your account tier.
Roon is working hard to implement built-in solutions for autoconfiguration of port forwarding even on accounts with CG-NAT. In the meantime, VPNs or other #tinkering solutions should allow for ARC to function with cellular data outside the home: Success with Tailscale VPN