Why am I not getting accessory ASINs from the product lookup api?

According to the AWS API documentation I should be able to fetch the ASINs for accessories for a given ASIN using the "Accessories" response group. I've been playing with the api scratchpad for a couple of days and putting in products I know should have recommended accessories but I have yet to get any accessories in the xml response.

Here is the response for a test request i did against a 4k television. You can see in the request arguments that I have ResponseGroup set to Accessories but there is no accessories node in the response:

<?xml version="1.0" ?>
<ItemLookupResponse xmlns="http://ift.tt/JgRJni">
<OperationRequest>
    <HTTPHeaders>
        <Header Name="UserAgent" Value="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.90 Safari/537.36"/>
    </HTTPHeaders>
    <RequestId>cbeccf4c-9507-4c0f-be26-9bfa7a6bdb83</RequestId>
    <Arguments>
        <Argument Name="AWSAccessKeyId" Value="<OMITTED>"/>
        <Argument Name="AssociateTag" Value="<OMITTED>"/>
        <Argument Name="Condition" Value="All"/>
        <Argument Name="IdType" Value="ASIN"/>
        <Argument Name="ItemId" Value="B00U9U9GII"/>
        <Argument Name="Operation" Value="ItemLookup"/>
        <Argument Name="ResponseGroup" Value="Accessories"/>
        <Argument Name="Service" Value="AWSECommerceService"/>
        <Argument Name="Timestamp" Value="2015-04-27T18:10:24.000Z"/>
        <Argument Name="Version" Value="2011-08-01"/>
        <Argument Name="Signature" Value="<OMITTED>"/>
    </Arguments>
    <RequestProcessingTime>0.0108810000000000</RequestProcessingTime>
</OperationRequest>
<Items>
    <Request>
        <IsValid>True</IsValid>
        <ItemLookupRequest>
            <Condition>All</Condition>
            <IdType>ASIN</IdType>
            <ItemId>B00U9U9GII</ItemId>
            <ResponseGroup>Accessories</ResponseGroup>
            <VariationPage>All</VariationPage>
        </ItemLookupRequest>
    </Request>
    <Item>
        <ASIN>B00U9U9GII</ASIN>
        <ParentASIN>B00WCIJ504</ParentASIN>
    </Item>
</Items>

What am I missing?