Thanks for fast answer.
Roon server used to run on my Mac Mini M1.
I am reading Roon Software Optimization - Potential Issues & Solutions (build 1353) and think I’ll have to re-download Roon.
There was a Mac OS update as well recently…
Edit: I followed the above by reinstalling Roon on Mac Mini M1 and the server reappeared in the top bar and is reachable across my network.