When SKUs are created in your Catalog and sent to the channel marketplace as product listings, Zentail sends multiple feeds to that marketplace, including a price feed, product feed, and inventory feed. 

Because Zentail sends multiple feeds to Amazon, sometimes Amazon will process one before the other, and return a Listing Error that the SKU is not in the Amazon Catalog:

 The listing error from this screenshot is for the price feed that Zentail sent to Amazon (as indicated by the "_POST_PRODUCT_PRICING_DATA_" message). 

In this case, Amazon processed & responded to the price feed first, specifically before the product feed (which is what actually creates the SKU on your Seller Central).

When that happens, Zentail automatically re-sends the feeds, so there is no action needed on your part. 

Other variations of this Listing Error could be that Amazon processes and responds to the inventory feed before the product feed. Regardless, this particular Listing Error will be automatically removed the next time Zentail re-sends the feeds for your products.