Could you give us a link to your site? You can publish a free, temporary site on businesscatalyst, using the „Publish“ button top right in Muse‘s application window.
Is this garamond pro, too?
Take care to click the menu item, two times so you see the "normal" state on the left hand side and the "text" on the right hand side.
Then you can change. In my case Garamond Pro seems to be a system font but not a webfont.
This is indicated by this tine little T with a landscape icon. This shows, it will be handled like an image instead of a font.
Watch in preview, how the button gets smaller and more and more unreadable when the browser gets smaller.
Take care to use a webfont. Better for SEO as well.