This is a very, very wild guess:
City of Ember (2008)
IMDb synopsis: For generations, the people of the City of Ember have flourished in an amazing world of glittering lights. But Ember's once powerful generator is failing, and the great lamps that illuminate the city are starting to flicker. When mankind is about to come to an end, a group of scientists decide to create and populate a city deep underground. Ember is to last for 200 years, after which its inhabitants are to retrieve from a strong box instructions to return to the surface. Over time, the message is lost, and life in Ember is rapidly deteriorating. Their power supply is failing, and food is being rationed. It's left to two young adults to unearth the secret of Ember and to lead the way out.