Lynn, thank-you for your response.

This seems to be an ongoing issue with the Medium group of sites as I have encountered the issue on a regular basis. The problem is that not every reader has the tech know how to realise and resolve the issue and many just dismiss the author/site as providing bad code which does nobody any good.

The one solution for authors that I have seen that will work reliably is to post the code example(s) on a hosting site such as github (possibly as a gist) and provide a download link.

Steve