Schema Product Error using EDD

Hello,
Overall RankMath is awesome.

But I am facing an issue in schema since months, and unable to solve, can you please help.

https://ibb.co/XLJtf2V

It shows me the following warning
brand
The brand field is recommended. Please provide a value if available.
warningdescription
The description field is recommended. Please provide a value if available.
warningimage
The image field is recommended. Please provide a value if available.
warningoffers
The offers field is recommended. Please provide a value if available.
warningsku
The sku field is recommended. Please provide a value if available.
warning
This product is missing a global identifier (e.g. isbn, mpn or gtin8). Please see documentation for valid identifiers.

I have added the following in activated theme functions.php too
But still getting the same errors.

//Schema Code Starts
add_filter( ‘rank_math/snippet/rich_snippet_product_entity’, function( $entity ) {
$entity[‘brand’] = ‘My Brand Name’;
$entity[‘offers’][‘priceValidUntil’] = ‘2025-12-31’;
$entity[‘offers’][‘availability’] = ‘http://schema.org/InStock’;
$entity[‘aggregateRating’][‘ratingValue’] = ‘4.9’;
$entity[‘aggregateRating’][‘reviewCount’] = ’19’;
$entity[‘review’][‘reviewRating’][‘ratingValue’] = ‘4.9’;
$entity[‘review’][‘reviewRating’][‘bestRating’] = ‘5’;
$entity[‘gtin8’] = ‘26598751’;
$entity[‘review’][‘author’][‘name’] = ‘MyName’;
return $entity;
});

Your Help would be highly appreciated.

Thanks
Abdullah