Thank you for your post. Do you see RoonServer running in the background in the menu bar or Activity Monitor on this Mac?
Diagnostics indicate that you’re using an old build of Roon on both server and client in this setup. Please first try updating to the latest available build. You can install the latest build without opening Roon by renaming your database folder - however, only take this step if you have a reliable Backup available, since it effectively “factory resets” your Roon environment.