Issue: Revit could not find analytical space that is necessary for energy simulation.
Solution: Simplify the complexity of the model. See Energy Analysis using Building Elements - Model Validation.
Solution: Add room bounding elements. See Room-Bounding Elements and Room Boundaries.
Solution: Check to ensure that building elements belong to the project phase set in the Detailed Model Settings in the Energy Settings dialog.
Solution: Check to ensure building elements form a generally enclosed shell. For example, there should be no missing walls, floors, roofs, windows, etc. See Energy Analysis using Building Elements - Model Validation.