Be sure you are applying 3D Invigorator to a Comp-sized Solid. If the Solid is not comp-sized, then the objects that you create may fall outside the comp preview window. In addition, when you first apply 3D Invigorator, you will see a 3D Invigorator start-up screen. If you click "Create a New Scene", then you will have an empty scene until you go into the 3D Invigorator interface to create your objects. Then, after you are finished creating all the objects, click the "OK" button and you will be able to see all the objects in the After Effects Composition window.
If you are still having issues, please describe what steps you are doing, and which scene preview window you are looking at.