Some elements are not sized because the system calculation is flow only. You may change the system calculation level to size them again.
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 26.4.0.0 (26.4.0.0)
Syntax
C#
public static FailureDefinitionId SizingCalculationFlowOnlyWarn { get; }