[theducks]

There is no src called out, telling it to use an embedded font

Here is a typical entry without all the mso crap (that probbly is meaningless to many devices)

@font-face {
font-family: "Charis";
font-style: normal;
font-weight: normal;
src:url(../Fonts/CharisSILR.ttf);    <<< this is your NORMAL font use
}

If you use Bold, you need a second @ font for the Bold weight and bold Font file
Have a Italic use, another @font and font file

Have bold Italic use? you guessed it, another set