I think if Dorico is in the foreground, it will never allow your computer to sleep because the audio engine keeps it awake. If you put Dorico to the background, then if you switch on the ‘Suspend audio device in the background’ option in Preferences, I think that will allow it, but we have encountered some problems with having this preference set, so I wouldn’t really recommend it. Unless you’re working with some completely enormous sound template that takes multiple minutes to load up, I’d recommend that you simply quit Dorico if you’re not using it, since Dorico itself only takes a few seconds to start up.