Metadata Retrieve missing files

Question

I am having an issue when retrieving a package using the Metadata API. I am trying to retrieve a package that has a flow in it. Here is a sample request:

<soapenv:Envelope
    xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
    xmlns:met="http://soap.sforce.com/2006/04/metadata"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <soapenv:Header>
        <met:CallOptions>
            <met:client></met:client>
        </met:CallOptions>
        <met:SessionHeader>
            <met:sessionId>**redacted**</met:sessionId>
        </met:SessionHeader>
    </soapenv:Header>
    <soapenv:Body>
        <met:retrieve>
            <met:retrieveRequest>
                <met:packageNames>Update Opportunity Partner Field Hierarchy</met:packageNames>
                <met:singlePackage>true</met:singlePackage>
            </met:retrieveRequest>
        </met:retrieve>
    </soapenv:Body>
</soapenv:Envelope>

The resulting zip file only contains a package.xml instead of also including the Flow contained in the package. When I do the same exact operation in Workbench, the zipfile they give back includes the file. Can anyone tell me what I am doing wrong?

Answer 1

Figured out the issue thanks to Not able to retrieve Settings through Metadata API

I needed to specify the apiVersion in my retrieveRequest, as it was defaulting to version 12.0 when not included.