If you import a reference scene into your Modo scene more than once (ie. the same filename reference scene is loaded two or more times), then there is a bug in Modo where the geometry from the scene reference scene is not available.
This problem exists on Modo10 and Modo11, but not Modo901/902.
To get around this problem, make a copy of the reference scene, and load the original reference scene, and then load the copy of the reference scene, and the scene will then render correctly.
I have reported this issue to Foundry.