Can't display Mapbox maps in Dash / plotly.graph_objs app

Dash Python
1

Hello. New here and trying to get a proper map (preferably the sattelite-streets version) within my Dash app. It is working to display the world map, and zoom to include data points in a particular country. But the map is just a very basic line outline of all the countries - no details at all. Here is the code snippet where I’m trying to load the map. The token I am using has been tested and works.

        mapbox_access_token = open(".mapbox_token").read()
        layout = go.Layout(
            margin=dict(l=20, r=10, t=20, b=20),
            height=map_height,
            geo=dict(
                showland=True,
                landcolor="rgb(250, 250, 250)",
                showcountries=True
            ),
            showlegend=False
        )
        retval = go.Figure(data=data, layout=layout)
        retval.update_layout(
            hovermode='closest',
            mapbox=dict(
                accesstoken=mapbox_access_token)
        )
        retval.update_layout(mapbox_style='satellite-streets')  # 'satellite'
        retval.update_geos(fitbounds="locations")
    return retval   # (retval is a go.Figure)

Any suggestions very much appreciated.