How can I show subtitle under title in single product page

I’m using OceanWp and WooCommerce. I’ve used Kia subtitle plugin to show subtitle of the product in Archive page and it worked. I’m trying right now to show the subtitle also in single product page under the product title. I’ve used this hook but it didn’t work

function kia_add_subtitle_to_single_product(){
    if( function_exists( 'the_subtitle' ) ) the_subtitle( '<h4 class="subtitle">', '</h4>' );
}
add_action( 'ocean_after_single_product_title', 'kia_add_subtitle_to_single_product', 20 );