Shadows are visible by default but they can be hidden using the Hide Shadows command. You can display the hidden Shadows again using the Show Shadows command of the View menu.
Select the Show command from the View menu by clicking on it.
Then select Show Shadows from the Show sub-menu.
This will display all the shadows in the floor plan again.
Note: When plans are emailed, all objects will be displayed when the recipient opens the plan even if the object type has been set to Hide.