Apple Maps shows only a grid on Mac Mini.
I see this is a fairly common problem - judging from the number of posts regarding it - that has not been solved so far. It appears - at least in my case - to be a problem on the user side, isolated to a particular device. My iMac, iPhone and iPad show all maps properly, only the Mac Mini shows a grid instead.
Is this something Apple doesn't like to talk about; and even less working on?
Mac mini, macOS 10.14