No matter how many times I turn on Nightshift, it keeps turning itself off.
I only ever use the "custom" time range, not the "by timezone" range. Perhaps there is a bug with this setting, instead of location-based timezone?
I currently have it set to
7:09pm to 7:00am
10.14.5 (18F203) but the problem has been happening for most of Mojave, if not all of it.
I haven't reinstalled macOS or made an OS update during this time. I may have rebooted – but I can't understand why rebooting should disable my preference setting!