If you deleted an Embedded font, then added a replacement, then that is what your book has access to.
unless you @font-face is having it look at your file system
Wrong path CaSe is a common goof.
TTF won't work for this book, it must be ttf. This book has the folder fonts not Fonts
Code:
@font-face {
font-family: "Great Vibes";
font-weight: normal;
font-style: normal;
src: url(fonts/00005.ttf);
}