Roon says Roon Arc is working but it won't connect

Try turning off IPv6 in your router - that seems to have been the trick for at least one brand of router…

Edit: although now I see that you’re using Starlink - where IPv6 is a requirement - so perhaps the trick for you is to see if port forwarding can be done for IPv6 (which I think is actually a contradiction in terms - so frankly, I’m just guessing…)