Information displayed by the application when we want to save the project.
Most likely, the project has another surface drawn on which no panel has been generated. You should go back to the Draw areas step and delete the unnecessary surface.
Returning to the Draw areas tab, we can see that we have created a surface that is too narrow for PV panels to be generated on it. The program does not allow you to save a visualization with no generated panels on any surface.
We need to delete this surface and then we can save the visualization.