Your document contained a Massing element which has been upgraded to a Mass instance. Please review the documentation on the new enhanced Mass capabilities to understand the implications of this change.
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 25.3.0.0 (25.3.0.0)
Syntax
C#
public static FailureDefinitionId UpgradedMassingWarning { get; }