Choropleth Map with plotly.express doesn't show map, just legend

I copied the “Indexing by GeoJSON Properties” example as seen on the Choropleth Maps in Python page. The code was executed with no error but there was no map showing, only the legend. In addition, the ‘box’, ‘pan’, ‘zoom’ options show but don’t work. I have the latest plotly version, installed via pip. any ideas? Thanks.