WordPress 3.9 includes the TinyMCE editor 4 version update which marks big changes in the API editor. Though the shortcodes are working in the front end as usual, the button shortcode from the visual editor is currently not displayed. This will be fixed in our future theme updates which will be announced via newsletter, so, make sure you are subscribed.
UPDATE: the shortcode button missing issue caused by WordPress 3.9 changes has been fixed. Please, update your themes to their latest versions.