**** Используйте этот крючок woocommerce ****
add_action( 'woocommerce_after_single_product', 'prev_next_product' );
add_action( 'woocommerce_after_single_product', 'prev_next_product' );
function prev_next_product(){
echo '<div class="prev_next_buttons">';
// 'product_cat' will make sure to return next/prev from current category
$previous = next_post_link('%link', '← PREVIOUS', TRUE, ' ', 'product_cat');
$next = previous_post_link('%link', 'NEXT →', TRUE, ' ', 'product_cat');
echo $previous;
echo $next;
echo '</div>';
}