It looks like you are trying to apply a shortcode to the title field. That is not supported by itself (only shortcodes in the post content are evaluated automatically), but easily remedied by adding it as a filter to get_the_tile in your plugin:
add_filter ('the_title', 'do_shortcode');
(I’m assuming that you ruled out other possible problems by running your shortcode in the content field and establishing that it works properly there)
EDITED The filter is in the function get_the_title, but its name is the_title.