You need to be on an entity to see the visualizations. Depending on the screen size content that is normally on the right hand side may become invisible. Clicking the same button hides the visualization area and brings back the content area.
If you are browsing the foundation you'll see the visualization of the foundation and similarly if you're browsing a linearization you'll see the visualization of the linearization that you're browsing
There are several buttons that you can use to decide how the visualizations appear. You need
If used, the system will show you the foundation but highlighting the linearization within the foundation using various colors and styles so that you can easly see which entities are in the linearization, which are not, which of the parents is the linearization parent, etc.