<?php

add_action( 'woocommerce_single_product_summary', 'seller_name_on_single', 11 );
     function seller_name_on_single(){
               global $product;
        $seller = get_post_field( 'post_author', $product->get_id());
        $author  = get_user_by( 'id', $seller );

        $store_info = dokan_get_store_info( $author->ID );

        if ( !empty( $store_info['store_name'] ) ) { ?>
            <span class="details">
                    <?php printf( 'Sold by: <a href="%s">%s</a>', dokan_get_store_url( $author->ID ), $author->display_name ); ?>
                </span>
            <?php
        }
     }
?>