Bit of an necro here, but:
Forest1 is looking for something called DataLayer which is in the engine content rather than your main content file. Do you have “exclude editor content when cooking” enabled under your project settings/ packaging? If so, the level is looking for an object which has been excluded from the build, and so it throws an error. I would recommend either unchecking that setting, or better yet replacing that asset with one from the main content directory.