[Siavahda]

Neither code worked.

Under Fonts in the left-hand menu of the Calibre Editor, there's four fonts. They all start CourierPrime - CourierPrime-Bold etc. I didn't name them that, they downloaded that way, so as far as I know that should be in their metadata as well?

In the Manage Fonts menu, Courier Prime shows as embedded. Monospace (which appeared there after I tried one of the codes Sirtel and JSWolf suggested, I didn't notice which) is also listed, but there's no tick to say it's embedded.

The start of my stylesheet looks like this

@font-face {
  src: url(CourierPrime-Bold.ttf);
  font-family: "Courier Prime";
  font-weight: bold;
  font-style: normal;
  font-stretch: normal;
  }

@font-face {
  src: url(CourierPrime-BoldItalic.ttf);
  font-family: "Courier Prime";
  font-weight: bold;
  font-style: italic;
  font-stretch: normal;
  }

@font-face {
  src: url(CourierPrime-Italic.ttf);
  font-family: "Courier Prime";
  font-weight: normal;
  font-style: italic;
  font-stretch: normal;
  }

@font-face {
  src: url(CourierPrime-Regular.ttf);
  font-family: "Courier Prime";
  font-weight: normal;
  font-style: normal;
  font-stretch: normal;
  }

I'm not sure what else to check or share here.