Move product attributes after summary on single product page

The list_attributes is a method of WC_Product class called with -> operator and the wc_display_product_attributes is a simple function.

This will fix the issue:

add_action ( 'woocommerce_product_meta_start', 'show_attributes', 25 );
function show_attributes() {
  global $product;
  wc_display_product_attributes( $product );
}