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When listing a product via Trading API or Inventory API with an ePID obtained from eBay site or Trading API’s GetItem, you may get a warning message in the API response:
21920205 – The product with ePID value <xxxxxxxxxx> is not currently listable. It has been dropped from the listing.
eBay database contains a large catalog. Not all catalog products can be used for listing. You may run into the above warning message even if the product is viewable on the site via https://www.ebay.com/p/xxxxxxxxxx, or returned via getProduct API call.
To find an ePID that is adoptable via the selling flow, please use Catalog API’s search or Shopping API’s FindProducts* call using keyword, GTIN, category. All ePID recommendations returned from these calls are adoptable via Trading / Inventory API selling flow.