There are undefined Rooms in the model! Recommend creating a Room schedule and checking the Area parameter of each Room for warnings.
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 26.1.0.0 (26.1.0.34)
Syntax
C#
public static FailureDefinitionId UndefinedRooms { get; }