Google recently announced a unique product feed specification as part of their ongoing efforts to improve product data quality on Google Shopping. The changes effect all accounts in the US, France, Germany, and the United Kingdom.
The enforcement of the new specifications has already started and will continue to ramp up over the next few weeks. By September, Google will be rejecting all violating offers which will result in the ads not being served through the Product Listing Ads (PLAs).
For more information, review the product identifier requirements and the product feed specifications here.
Unique Product Identifier Requirements
Unique Product Feed Specifications
Eugene O'Rourke