The port forwarding is irrelevant in the local network. If forwards ports from the outside to the (local) inside.
Are your only Roon apps the regular Remote and ARC, both on the iPhone and neither can connect? Do you have any other Roon remotes on any other devices (PC?) that you can try?
My initial guess is that either the iPhone is not connected to your home wifi or that somehow the wifi network has become a different network than the wired one where the PC is. On the latter: Roon cannot traverse networks. In most cases, the router configures the wifi and the wired network as one network. However, there is often an option in the router settings that separates them into two. Maybe this got flipped somehow.
The issue turned out to be the Windows 11 Firewall Public Network portion.
When I added in Roon to be allowed through for Public Network both the internal and the external network access started working.
The internal network access was already on.