If you've ever used the SNOOZ app, the night light could be turned on. You can turn this off by opening the app, clicking the light icon, and setting the level to "Off."
Alternatively, you can perform a hard reset on the device by following these steps.*
1) Turn SNOOZ on
2) Simultaneously press the volume up and down buttons for 5 seconds until SNOOZ shuts off
3) Turn SNOOZ back on and see if the problem persists
*Please note the hard reset will delete any timers you have set with the scheduler.