School Administrators and Training Site Administrators mutually confirm that students at a specific program are approved to apply to a specific track offered by a site.
Students can only see site and track listings in the Directory which have been approved for them. Students cannot select tracks for ranking in the match if the track-program relationship has not been approved.
Sometimes sites also choose to delete hiring tracks if they no longer wish to hire into them, and that's another reason a track might disappear. Contact your school administrator or the site directly for more information.