@hube2 yes, it’s kind of hard to know what it refers to, my guess is the order ID of the WC order that was just placed.
@squatter1 I would rule out that your hooked function is being called, try this below the function definition:
var_dump( $order_id );
var_dump( $old_status );
var_dump( $new_status );
wp_die( var_dump( order ) );
Do you get any output? (remember to set this in wp-config.php):
define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', true);