You might encounter an error referencing an invalid postal code when trying to list a new product.
First try to resolve the issue by checking that city, state, and zip code are filled in the address field for the warehouse used for eBay on your Account Settings.
-Note: these fields are different from the "eBay Location" field for each warehouse within Zentail. Zentail will try to send the Postal Code for your warehouse to eBay unless you have an eBay Location field filled in.
We also found that it may be related to the shipping policy, if you are using shipping_default vs shipping_FBA on eBay.
We suggest changing the shipping policy to shipping_FBA in Zentail and directly on eBay.