functions - Why is the term of my current page not returning a slug?

Why is the term of my current page (custom taxonomy) not returning a slug? I have managed to get the following returned in my URL:

0, Array, '/{empty space}/

I am trying to pass the custom taxonomy term into my $args array object property rewrite. Could someone please explain to me what I am doing wrong? I have looked at many other posts on how to retrieve the current page custom taxonomy term and have already tried to implement the proposed solutions. Right now I'm at a total loss. The code below currently returns /connect/series//destination_page.

How can I get the current page taxonomy term to appear in-between the two //?

// Registers a new post type
add_action( 'init', 'message_init' );
function message_init() {

    // Get the queried object and sanitize it
    $current_page = sanitize_post( $GLOBALS['wp_the_query']->get_queried_object() );

    // Get the page slug
    $slug = $current_page->post_name;

    $args = array(
        'public'             => true,
        'publicly_queryable' => true,
        'show_ui'            => true,
        'show_in_menu'       => true,
        'query_var'          => true,
        'rewrite'            => array( 'slug' => 'connect/series/'. $slug),
        'capability_type'    => 'post',
        'has_archive'        => true,
        'hierarchical'       => false,
        'menu_position'      => null,
        'supports'           => array( 'title', 'editor', 'author', 'thumbnail' ),
        'taxonomies'         => array( 'category' )
    );

    register_post_type( 'message', $args );

}