Export fields woocommerce

Hello,
I am trying to export content of custom fields created with ACF with Woocommerce product exporter / importer.
I have put the following code in my function file:

function add_export_column( $columns ) {

// column slug => column name
$columns[‘marca’] = ‘Marca’;

return $columns;
}
add_filter( ‘woocommerce_product_export_column_names’, ‘add_export_column’ );
add_filter( ‘woocommerce_product_export_product_default_columns’, ‘add_export_column’ );

function add_export_data( $value, $product ) {
$value = get_field(‘marca’);
return $value;
}

add_filter( ‘woocommerce_product_export_product_column_custom_column’, ‘add_export_data’, 10, 2 );

—-
But it’s not working.
Someone could help me?

Thanks in advance