When I make an AddItem call, I keep getting "The region number you have entered is invalid. Please enter valid region." As far as I know, I'm not passing a region number. What's going on here?
This issue is caused by including a <PostalCode> that doesn't match the selected <Country> in the AddItem request. For instance, if you specify a postal code of 95125 and a country of Hong Kong (HK), eBay will try to match that postal code with HK, which is not a valid scenario. Per the documentation: