My nav screen thinks it's almost always night. Even on the sunniest days, I go under a bridge and it's night mode. On cloudy days, it's night again. I asked the dealer about it. He gave me this funny look, as if I had suddenly began speaking in Swahili.
Mine does the same thing - Darkens when I go under a bridge, park in the garage, in a tunnel ... It seems to be very sensitive to light changes. There IS an option in the settings to Turn off the Day/Night - but then it would be way too bright at night. Ideally they should have a Sensitivity Setting included.
Check your manual settings (leftmost button underneath steering). Mine is OK, but still remember when I got my new ICE car a few years back, couldn't figure out why my dash lights were always on bright and didn't change with day/night. Turns out if the setting is on Max, that is what happens. Learned that on a forum, too, as others were similarly baffled. Anyway, might not be the same with the Kona, but no effort to check to make sure.
Dealer's staff are not technicians, nor engineers. They only exist as unwanted brokers in the sales transaction. Tesla has the right idea.