The source – support.google.com
Google Merchant Center can reject an item if any unique identifier, especially the GTIN code, is not listed correctly. For now, this applies to paid ads, but will soon apply to information posted for free as well.
On September 15, 2021, Merchant Center will start counting items in free ads that have the same GTIN code and variant attribute values as repeatable items.
The attributes in question are:
- for all categories: "condition" [condition] and "multipack" [multipack];
- for clothing items: "color" [color] and "size" [size].
If repetitive items are found, only one of them will be placed for free, and the others will be rejected.