Google has updated its policy where an identifier exists issue will no longer lead to disapproval of your product listings. Instead, Google will first issue you a warning for identifier exists.
Google explained that "Unique product identifiers (UPIs) define the product you're selling in the global marketplace. They uniquely distinguish products you're selling and help match search queries with your products."
Previously, this would have led to your product listing being disapproved, that is if they were submitted indicating an identifier does not exist for the product, but there is evidence that a unique product identifier exists.
"After this change the offers with the Item issue Incorrect value: identifier exists [identifier_exists] will receive a warning instead of a disapproval. If product identifier requirements are not met, then your item’s performance may be limited," Google explained.
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