I tried taking a photo tonight to show someone how night mode works on my phone, but it just took a 'normal' photo. I went over to the wide angle lens and that worked. I restarted the phone and both lenses worked.
I slid over to normal mode to take a picture and back to night mode, to compare to the regular lens, once again, did not work. Only the wide angle worled.
My guess would be, this started after the most recent update, but I just noticed now since I don't don't night mode shots that regularly.