Description
Since the generation of the diagram, dirty areas may have appeared on network features related to some diagram features, or the network topology has been validated either on an extent that intersects the diagram geographic area or after editing utility network objects that are used in the diagram.
Solution
Verify that there are no dirty areas on network features represented in the diagram, regardless of whether those features are visible or aggregated in the diagram. If such network features exist, validate the network topology first.
Then, update the network diagram and run the tool again.