I was able to get attributes from the attached slpk using our unity sample. Are you not getting results for any building?
The only suggestion I have right now is to set the origin of the map to be close to the layer, if you haven't done so already. Due to the lack of double precision in Unity, the raycast can be imprecise when the buildings are too far from the scene origin.
Thanks a lot @AShahbaz for your data validation !
i revised my code. It was a problem with conversion between an arcgis dictionnary and a json array with the type ArcGIS Date....
Rémy