Issue: Conceptual mass energy analysis cannot be performed unless the mass has one or more mass floors, and the energy analytical model is enabled.
Solution: Click Yes to proceed with the analysis. Revit will create a mass floor using the lowest project level for visible masses, enable the Energy Analytical Model, and run the simulation.
Click No to cancel the analysis request.
After the analysis is complete, the changes are removed from the project. See Energy Analysis using Conceptual Masses - Enable the Energy Model.