The screen is not lit, perhaps an issue with the proximity sensor?

The screen will not light to it's normal brightness. I can still see and use the screen, but not without straining my eyes or very low light. I think it may have to do with the proximity sensor dimming the display. I downloaded an app to check if the sensor was working properly, and it appears to be fine. It registers when something is nearby properly. I've done multiple restarts using the power button and the down volume key at the same time, but no results. I've also booted into safe mode to see if it was any recently installed apps, but again, no luck.