In ArcMap Desktop, I can configure symbology for my layer by concatenating two different fields, then successfully publish the symbolized/categorized layer to ArcGIS Online as a hosted feature service. Example concept snipped and attached.
In ArcGIS Pro, when I configure symbology based on categories formed using an expression (combining two different field attributes), I get this error:
The only "fix" is to publish this categorized data through ArcMap Desktop OR to publish using "show location only" in ArcGIS Pro (simple rendering) and re-symbolize in ArcGIS Online once published using an expression.
Please allow ArcGIS Pro the same rendering support as ArcMap so we can publish categorized WebLayers through ArcPro rather than ArcGIS Desktop or using simple renderer.