The designer should inspect the view's Visibility/Graphics settings. Area Lines, also referred to as Area Boundary Lines, are view-specific elements whose visibility can be controlled by the active view, an applied view template, or category-level visibility settings. If the applicable line category is disabled, Revit can create the boundaries successfully while warning that the newly created elements are not visible in the current Area Plan.

The review should include the Model Categories and Annotation Categories tabs, any active view filters, temporary hide/isolate status, and the view template controlling the Area Plan. Where a template governs visibility, the correction should normally be made in the template rather than as an isolated view override, particularly when the same standard must apply to multiple Area Plans.

A Plan Region changes the local view range and does not govern Area Boundary Line visibility. Detail Level affects how certain model geometry is represented but does not normally suppress Area Lines. The Area Scheme determines the type and organizational purpose of an Area Plan, such as Gross Building or Rentable Area, but it is not the direct location for correcting hidden linework.

Reference topics: Area Plans; Area Boundary Lines; Visibility/Graphics; view templates; view-specific elements; graphical troubleshooting.