Trying Drilldown Choropleth, tips needed for mapping in Power BI.

Hi, I am looking for tips to work on a project. I selected to make a multi-layer map visual using Drilldown Choropleth app in Power BI. This is first time using the app. I want to have a map go from state (US) to local (MSA boundary) with three levels of data-- layer for sites, shaded map for density, and distribution of demographic stats seen on hover. 

Currently, I am getting invalid json after using online available with a data model issue can't link on geo for map. How are the json files loaded? Do I need to start in a new workspace or can I fix the current? And, can you share reference material for Power BI mapping for multi-layer and Drilldown Choropleth?