Gtin in structured schema

Hello,

I have an issue with structured schema for Google, I only use variation products.

I tested with this two codes and in the test of schema.org I have GTIN13 ”False” but the GTIN are true in my back office :

add_filter( ‘rank_math/snippet/rich_snippet_product_entity’, function( $entity ) {
$entity[‘gtin13’] = get_post_meta( $variation[‘variation_id’], ‘hwp_var_gtin’, 1 );
return $entity;
});

get_post_meta( $post_id, ‘hwp_product_gtin’, 1 );

add_filter( ‘rank_math/snippet/rich_snippet_product_entity’, function( $entity ) {
$entity[‘gtin13’] = get_post_meta( $post_id, ‘hwp_product_gtin’, 1 );
return $entity;
});

Thanks in advance

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