Thank you for your patience, and please accept my apologies that it’s taken us this long to respond to your request for assistance.
I hope you don’t mind - to protect your internet privacy, I’ve removed the screenshot from your public post after noting its contents.
The diagnostics you’ve provided suggest that there is a layer of network address translation (NAT) in your local network blocking the Core from reaching the broader internet.
Try to manually open the port in your modem/router’s port forwarding configuration.
Make sure the IP/Port matches the Port listed in Roon → Settings → ARC.
If you are using a second router, then check if your HOTBOX modem is in Bridge mode (instructions here)
If these steps are not successful, it’s possible that the NAT layer is at the level of your internet service provider. I recommend reaching out to HOT Fibre directly and asking the following questions:
Have you implemented carrier-grade NAT for my account level?
Have you fully implemented IPv6, or do you have IPv4 addresses available?
Can I request a static IPv4 address to support port forwarding?
Are there any ports you have reserved at the ISP level I should be aware of?
We’ll be watching for your response. Thank you again for your patience.