Custom taxonomy labels won’t display

Try changing 'labels' to an array arg, and passing that. Also, check for syntax:

$labels => array(
    'name' => _x( 'Seminar Types', 'taxonomy general name' ),
    'singular_name' => _x( 'Seminar Type', 'taxonomy singular name' ),
    'search_items' => __( 'Search Seminar Types' ),
    'popular_items' => __( 'Popular Seminar Types' ),
    'all_items' => __( 'All Seminar Types' ),
    'edit_item' => __( 'Edit Seminar Type' ),
    'update_item' => __( 'Update Seminar Type' ),
    'add_new_item' => __( 'Add New Seminar Type' ),
    'new_item_name' => __( 'New Seminar Type' ),
    'separate_items_with_commas' => __( 'Separate seminar types with commas' ),
    'add_or_remove_items' => __( 'Add or remove seminar types' ),
    'choose_from_most_used' => __( 'Choose from the most popular seminar types' )
);
// Set up the Types arguments
$types_args = array( 
    'rewrite' => array(
        'slug' => 'seminar-type',
        'with_front' => 'false'
    ),
    'labels' => $args
);
// Register the Seminar Types taxonomy
register_taxonomy( 'cemb_seminar_type', array( 'cemb_seminar' ), $types_args );