Hi Frederick!
Thanks for contacting us with your question!
This is a known bug in Highcharts maps. You can find a related GitHub ticket here:
https://github.com/highcharts/highcharts/issues/17086 To show
maplines on the chart, just use TopoJSON map, instead of GeoJSON map. In your case, it leads to the next issue: in Highcharts ~9 TopoJSON maps have some bugs, so you will need to upgrade Highcharts in your project to release ~10, the best way - upgrade to the latest release, which is Highcharts v.10.2.1 (
https://www.highcharts.com/blog/changel ... ts-v10.2.1).
In the demo below, you can see an example of a US map with
mapline and
mappoint.
Demo: https://codesandbox.io/s/highcharts-rea ... ked-ec0omq
Let me know if you have any further questions.
Regards!