Hello,
Thank you for contacting the support, and sorry for any inconvenience that might have been caused due to that.
1. Brand
To fix the brand
warning, head over to WordPress Dashboard > Rank Math > General Settings > WooCommerce
and choose from any of the available fields to use as your product’s brands.

If you want to use a custom value for your Brands, you can do that by using the following code in your theme’s functions.php file:
// Add Brand for Products.
add_filter( 'rank_math/snippet/rich_snippet_product_entity', function( $entity ) {
$entity['brand'] = 'Rank Math;
return $entity;
});
Replace the “Rank Math” text with your actual brand name then run your website through the Structured Data Testing tool once again.
2. SKU
You can fix the SKU issue by heading to your product’s inventory as shown below:

Hope that helps and please do not hesitate to let us know if you need our assistance with anything else.
Thanks for the tips.
For the SKU, would that work if we didn’t enable stock management ?
https://prnt.sc/102hpf0
Hello,
Thank you for contacting the support, and sorry for any inconvenience that might have been caused due to that.
Disabling this option will still add the “SKU” warning in your Google Search Console as “SKU” and the option “Enable stock management at product level” are different settings.
If this option is disabled, you are responsible for updating the Stock Status. You can learn more about it here: https://docs.woocommerce.com/document/managing-products/#inventory-tab
Hope that helps and please do not hesitate to let us know if you need our assistance with anything else.
Hello,
If you do have another question in the future, please feel free to create a new forum topic, and it will be our pleasure to assist you again.
Thank you.