Monospaced fonts ignored in Kobo Aura

I have a science fiction book in which there are a lot of paragraphs in "machine code" for which I used a monospaced font "Courier New".

This font was in Sigil's Font Folder and also declared in the CSS stylesheet.

The Kobo Aura ignores this font and displays these paragraphs in the same font as the rest of the book.

I then removed all references to the "Courier New" font and nested these paragraphs in <code></code> but the font displayed is still the same as all the other paragraphs in the book.

I'm stumped.

Edit: I tried the book on my Kindle Keyboard and it works correctly.