Thank you for the login details. The FTP was not working, but it wasn’t needed.
The problem was that the shortcode was placed into a “Custom code” block on the front-page visual editor. I hope you don’t mind, but I have changed the type of that block to simply “Text” and put the shortcode there: https://i.imgur.com/QJJao41.png
Now it appears to be working correcly.
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