I'm using ArcGIS Portal 10.5.1, when I create a map service from a multipoint feature class, I can create a feature layer and select the Heat Map option. However, it never appears in the web map. No error appears, it just does not display anything. If I use a regular 'point' feature class, the heat map works as designed. Is a multipoint feature class not acceptable?
Same issue here. I have a very large point layer that must be multi-point. Heat mapping on this multipoint works in ArcGIS Pro but not in AGOL or Portal. Did you ever find a workaround?