Hierarchies can be removed when:
The Time Range property for the view changes. That change can impact time hierarchies and measure items.
The hierarchy or its dimension was removed from Stratum.Connector for Viewer and is no longer available to any users.
All time hierarchies will be removed from a view if you change the Time Range property from No to Yes. Changing the property to Yes lets you use measure items with time ranges in the view. In that case, time hierarchies are irrelevant and will be removed from the view.
Here is a view that has a Time Range property of No and a time hierarchy on columns.
Here is the view after the Time Range property was changed to Yes, and here is the related prompt that displayed to confirm the change. Time hierarchies were removed, as were all measure items (they did not have time ranges). Measure items with time ranges can be added to the view after this change to the Time Range property.
