Hello @luigi_GRILLI,
Try the following steps:
A) Close Roon on your Mac
B) Open Finder.app
C) In the Menubar go to Go > Go to Folder
D) Type in ~/Library/Roon/Database/Registry/Client and click “Go”
E) Delete all files begining with “GMS”
F) Empty the Trash
G) Restart Roon
I’ve included a recording of what this looks like:
-John