"array must have at least one stop" error on custom drilldown choropleth map

I've been trying to make a custom drilldown choropleth map as using Mapbox Visual as shown in this video here. However, when I enter values for Location and Color, I get the following error on the map:

"layers.choropleth.pain.fill-color.stops: array must have at least one stop"

I've searched for several versions of this error and haven't been able to find any information about it on Power BI forums or Mapbox forums. Any idea what's going on? As far as I can tell, my data is as it should be and I've followed the instructions in the video.