Oh alright, I misinterpreted your earlier post as the gameplay not working in a new level.
Ok so if the level is not displaying in the level selection menu, just make sure to first close the project, delete the Saved folder and restart it. This will ensure that any previously saved level data will not override the new information that you added. Usually this turns out to be the problem, but if not could you share a screenshot of the new element that you added in the Level Data Array?