Hi! I'm using "Almar" and this does not work for me either, I have manged to change the fonts for H1 H2 & H3, but not the navigation or the Buttons..
@font-face {
font-family: your-font-name;
src: url(enter your font name url here);
}
.Header-nav-item a {
font-family: your-font-name;
}