Create a site view as follows.
Revit site plan showing floor plan.
This issue occurs because there is an incorrect view range in the main view.
Draw the sketch as necessary then click finish.
In the new plan dialog clear do not duplicate existing views.
Under floor plan views select the level on which to base the site view.
About plan regions to define multiple cut planes within a plan view use plan regions.
You can find this tool in view tab create panel plan views drop down plan region.
Click view tab create panel plan views drop down floor plan.
About plan views in a 2d view display a floor plan a reflected ceiling plan or structural plan.
If the view range intersects the geometry of a level in your main view that level cannot be used as an underlay in the main view.
A floor or slab will be visible in a plan view if it is partially above the view depth or if it is within 4 feet approximately 1 21 meters of the bottom clip.
Open the site view.
Click view tab create panel plan views drop down floor plan.
Please like this video.
In this video i show you everything you need to.
When you tried to underlay a floor only doors and windows were visible.
Under floor plan views select the level on which to base the site view.
In the project browser rename the newly created floor plan view to site.
Get this revit file here.
In the new plan dialog clear do not duplicate existing views.