If I am understanding your question correctly, your are trying to get back to the Night Mode on the Display. This is not related to the GPS, but rather related to your dashboard lights setting (the adjusting wheel to the left of the steering wheel).

If your interior lights are turned all the way up, you cannot enter Night Mode. As long as you turned the lights down (you can feel a catch when the dashboards lights are on high). Once they are turned down off of high, you should be able to enter night mode again. (You may have to go to the display screen to turn the night mode option on---this doesn't turn it on, your headlights turning on changes it to night mode).

If this doesn't work, then I don't know what is going on.