Running Cura 3.2.13 on Debian GNU/Linux (Stretch)
Cura has a number of notifications that pop up when there is an error that requires user intervention/resolution, but there is no clear indicator/notification when no model is previously loaded in the Prepare view, when the user is then in the Monitor view.
The only indicator is a subtle one, insofar as the Start Print button disappears.
In this picture, mouse hovered over where Start Print normally is available to the user:
There are a number of ways we could indicate this to the user, or decide to leave as-is. This is a UI/UX question, but I think the current solution is inadequate.