I have created an app with appstudio, but the legend will not populate. I have used both a feature service and tiled service. The layers show but no legend. I am using the map viewer template in appstudio.
Can you please share your webmap with us? I would like to investigate the contents of the webmap.
Here is the webmap: http://flagstaff.maps.arcgis.com/home/item.html?id=01ca264aa34b499d9d84c4f17e741d07
I was able to get the legend to show by publishing the service to our server, but not hosting to AGOL.