Not sure if you’ve seen, in most cases this seems to help - there are a hundred threads about this, with servers and/or endpoints not being found:
It’s possible that it has to be repeated after a Roon update, reinstalling, or Roon Server restart, but it might also stick for other people. I can’t tell, and my own Mac (just remote, though) has zero problems.
I have to reboot my M1 MacBook Pro running my Roon Server after Roon updates itself. Otherwise it won’t see any endpoints apart from the one that is directly connected to it through USB. A reboot later and everything magically reappears.