I’m checking it against my Mac Pro with working iCloud. The Mac Mini is set up as a valid device on the appleid webpage, and it appears, with the Mac Pro in ‘Find Devices’ on icloud.com. When I look at the iCloud stats in System Prefs, it shows the same iCloud data size as on the Mac Pro. In fact, in every way I can think of checking, the 2 installations are exactly the same – the only difference seems to be that the iCloud content is not showing in the finder window on the Mini – nothing in user/library/mobile documents. I don’t know how to proceed from here.