Problem with LayerList visibility toggle

[KarenEllett]

I am trying to pull in a MapImageLayer and show a LayerList that will allow users to toggle the visibility of the sub layers.  I was hoping to do it this simply:

require([
   "esri/Map",
   "esri/views/MapView",
   "esri/layers/MapImageLayer",
   "esri/widgets/Print",
   "esri/widgets/LayerList"
   ],
   function(
      Map, MapView, MapImageLayer, Print, LayerList
      ){

      myApp.myLayer = new MapImageLayer({
         url: "https://server/arcgis/rest/services/Viewer/Layers/MapServer",
         title: "Layers",
         visible: true
      });
      myApp.map = new Map({basemap: "streets", layers:[myApp.myLayer]});
      myApp.view = new MapView({
        container: "viewDiv",
         map: myApp.map,
         zoom: 8,
        center: [-81.034814, 33.6],
      });

      myApp.view.when(function(){
         var layerList = new LayerList({
         view:myApp.view
      });
      myApp.view.ui.add(layerList, "bottom-right")
   })

});

However, I have a bunch of sublayers within sublayers in this map service.  It's arranged like this:

• Transmission
  • Energized Layers
    • Energized Substation
    • Energized Structure
  • Inactive Layers
    • Inactive Substation
    • Inactive Structure
• Distribution
  • Primary
  • Secondary
• Environmental

etc, etc.  I find I can toggle the visibility on the map service as a whole, or on the primary subgroup (Transmission, Distirbution, etc) But everything below that doesn't allow me to toggle....

Is there a setting somewhere that will let me do this? Or am I going to have to pull each and every one of these subgroups in individually??