that’s weird. So basically this happens if Lead-DBS (=Matlab) doesn’t have write access to either the directory in which Lead-DBS is installed or the user home. On OSX, usually, the home directory should be fine. So could be you installed lead-dbs on a drive with read-only permissions?
Another thing is that everything should still work fine but would use default preferences, i.e. ignore the user preferences. Did you modify prefs at all? You can do so by using the [Tools] menu (-> will migrate to [Preferences] menu soon) [Edit Preferences file…].
If you don’t need to edit any prefs and are happy with defaults you could just ignore the warning.
Hope this helps!