ArcGIS Online does not reflect the symbology of null values correctly when publishing from ArcMap.
Last Published: January 12, 2016ArcGIS Online
Bug ID Number
January 8, 2016
February 13, 2023
After review by the development team, it has been determined that this issue is related to a known limitation with the software that lies outside of Esri's control. The issue's Additional Information section may contain further explanation.
Currently, this particular workflow is supported in the REST model.