Hi @Ben_Katz,
Please forgive the radio silence - I saw that my colleague @benjamin was assisting you in a separate thread over here. Am I correct that basic functionality has returned to Roon?
Diagnostics indicate that Verizon likely has since assigned an IPv6 address to your account since you initially setup ARC. They are in the process of rolling out IPv6 for their residential-tier accounts, and other users have reported similar symptoms after Verizon silently reassigned their IP address. It might be worth checking on your FIOS web administration page if IPv6 is enabled here.
Unfortunately, ARC is not yet compatible with IPv6 in the main production release available to the public. However, we’re testing compatibility for IPv6 over in #early-access, our beta test group, if you’re interested in giving it a shot. You can join Early Access by following the steps on this page: https://help.roonlabs.com/portal/en/kb/articles/roon-early-access-program
Otherwise, I’m going to recommend a workaround that has restored functionality for users stranded by port forwarding failures: a third-party app called TailScale. You can learn more in this thread: Success with Tailscale VPN