Why do I get an error when trying to search by by a particular ItemId? (EAN)

When I do a search by item ID, I get an error saying my ItemId is not a valid value. the id I am using is
9780743273565.
Can anyone help me on this? I have been stumped for a while now. attach is my php file

here is my XML

ItemLookupResponse>
−
<OperationRequest>
−
<HTTPHeaders>
<Header Name="UserAgent" Value="Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2.6) Gecko/20100625 Firefox/3.6.6 (.NET CLR 3.5.30729)"/>
</HTTPHeaders>
<RequestId>c9ac4ddf-116c-4136-a5ae-ace9395cfd18</RequestId>
−
<Arguments>
<Argument Name="Operation" Value="ItemLookup"/>
<Argument Name="Service" Value="AWSECommerceService"/>
<Argument Name="AssociateTag" Value="affiliateTag"/>
<Argument Name="Version" Value="2009-10-01"/>
<Argument Name="region" Value="com"/>
<Argument Name="Signature" Value="5hyBW6g7hbCu/VrlUXYFKERY6osECu90h/3V/MWvILM="/>
<Argument Name="ItemId" Value="9780743273565"/>
<Argument Name="AWSAccessKeyId" Value="0XQ36T5736VESGZK91G2"/>
<Argument Name="Timestamp" Value="2010-07-22T17:23:07Z"/>
<Argument Name="ResponseGroup" Value="Large"/>
<Argument Name="MerchantID" Value="All"/>
<Argument Name="IDType" Value="EAN"/>
</Arguments>
<RequestProcessingTime>0.0083990000000000</RequestProcessingTime>
</OperationRequest>
−
<Items>
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<Request>
<IsValid>True</IsValid>
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<ItemLookupRequest>
<Condition>New</Condition>
<DeliveryMethod>Ship</DeliveryMethod>
<IdType>ASIN</IdType>
<MerchantId>Amazon</MerchantId>
<OfferPage>1</OfferPage>
<ItemId>9780743273565</ItemId>
<ResponseGroup>Large</ResponseGroup>
<ReviewPage>1</ReviewPage>
<ReviewSort>-SubmissionDate</ReviewSort>
<VariationPage>All</VariationPage>
</ItemLookupRequest>
−
<Errors>
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<Error>
<Code>AWS.InvalidParameterValue</Code>
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<Message>
9780743273565 is not a valid value for ItemId. Please change this value and retry your request.
</Message>
</Error>
</Errors>
</Request>
</Items>
</ItemLookupResponse>

 

I always use ASIN and not EAN... but I can't find the ASIN for this product. Try using the id from the url:

http://www.amazon.com/Great-Gatsby-F-Scott-Fitzgerald/dp/0743273567

i.e. 0743273567