I faced an issue in the Product API of AMAZON MWS where its displaying error country_of_origin=NULL and required error return by API.
A value is missing from one or more required columns from this group: [country_of_origin = null]. I found the solution for that, Hope it can help anyone searching for the same.
<Message>
<MessageID>1</MessageID>
<OperationType>Update</OperationType>
<Product>
<SKU>5678999993</SKU>
<StandardProductID>
<Type>ASIN</Type>
<Value>5678999993</Value>
</StandardProductID>
<ProductTaxCode>A_GEN_NOTAX</ProductTaxCode>
<DescriptionData>
<Title>MULE 3L - Racing Red/Pitch Blue</Title>
<Brand>CAMELBAK</Brand>
<Description>This is a test product description.</Description>
<BulletPoint>Perfect for hiking.</BulletPoint>
<BulletPoint>Bladder for hydration.</BulletPoint>
<MSRP currency="AUD">100.00</MSRP>
<Manufacturer>CAMELBAK</Manufacturer>
<ItemType>outdoor-backpacks</ItemType>
<CountryOfOrigin>US</CountryOfOrigin>
</DescriptionData>
<ProductData>
<Outdoors>
<ProductType>
<OutdoorRecreationProduct>
</OutdoorRecreationProduct>
</ProductType>
<VariationData>
</VariationData>
</Outdoors>
</ProductData>
</Product>
</Message>
Need to pass US , Country name should be in country code. and this attribute must need to add in the DescriptionData block of XML like above.