On my Windows 11 PC, that I have the Roon installed, the Roon controller will not work on that same computer. I have already allowed all the Roon programs to bypass the Windows firewall. The Roon controller works on Android phone though.
Describe your network setup
TP Link mesh wifi system. Roon PC is connected to the network through wifi 6, with one of the mesh's close to the PC.
Is Roon Remote on your android phone still working?
What happens if you select “Select a different Roon Server” in the Windows Roon application? It should, show you a list of the Roon servers that are currently running on your network - of which there should be only one - the one on the Windows PC.