Thank you, Rebeka, for your suggestions. The help link you quoted is known to me and I have set everything up to order (including setting permission for full disk access). My core is on my Mac Mini and my endpoint was my IMAC, this time. I just don’t understand why the problem with Mac /IOS devices regularly pops up- all my other devices (speakers / headphone amplifier and streamer) never cause trouble. I always have to spend a lot of time to find a solution/ this time I de/installed roon on my IMAC and then re/installed again. Wish Roon would run smoother.