Google announced that it will begin enforcing that Google Merchant Center merchants use Manufacturer Part Number (MPN) and accurate ones. Google said starting in August of 2021, item-level warnings for "Incorrect product identifier [mpn]" will be issued on the Diagnostics page of your Merchant Center account. Then in September of 2021 Google will disapprove merchants with these issues.
Google wrote the "Manufacturer Part Number (MPN) is a unique product identifier that is used to identify a specific product among all of the products produced by a manufacturer. Customers may search for a product using a specific MPN, so providing the MPN can help ensure that your product is shown in relevant situations."
So in August of 2021, item-level warnings for "Incorrect product identifier [mpn]" will be issued on the Diagnostics page of your Merchant Center account. These warnings are intended to notify you that you’ve submitted an incorrect value for the MPN [mpn] attribute for one or more of the products listed in your product data. Then starting in September of 2021, the products for which you received warnings will be disapproved.
Google said you should "review your Diagnostics page to see if your products are affected, and either provide a valid MPN value or clear the current incorrect value in your product data."
Forum discussion at Twitter.
