Weird, it was working fine right up until the update yesterday to 15.5 and now Dark Mode (Auto) doesn't switch over. I checked that location was turned on and Dark Mode was set to "Auto". I have Night Shift set from Sunrise to Sunset and it's dark outside so it should make the switch. So I set N.S. to Custom, from 9pm to 7am. It did not make the switch over until I selected Light then Auto, that's when Auto when the switch to Dark Mode. Weird, anyone else have a working solution? I may just have to switch over manually until it sorts itself out.