Message "line -1: Response is missing or empty" when submitting a POST message

Hi,

In SoapUI Open source, I'm trying to submit a REST web service call.  I was able to load the WSDL from my web service definition just fine.  I was able to create an authentication header that fixed my original authentication error.

The message I get is:

line -1: Response is missing or empty

Here's the web service call:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:shop="urn:microsoft-dynamics-schemas/codeunit/ShoppingCartMgt">
<soapenv:Header/>
<soapenv:Body>
<shop:PurchaseSingleItem>
<shop:customerNo>Cxxxxxx</shop:customerNo>
<shop:itemNo>Itemxxxxxx</shop:itemNo>
<shop:last4CC>0000</shop:last4CC>
<shop:cCLineNo>10000</shop:cCLineNo>
<shop:promoCode></shop:promoCode>
<shop:amount>999.00</shop:amount>
<shop:status></shop:status>
<shop:statusMsg></shop:statusMsg>
</shop:PurchaseSingleItem>
</soapenv:Body>
</soapenv:Envelope>

If I copy the WSDL and paste it into a browser, the web service call runs successfully.

I'm trying to understand the "Response is missing or empty" message.  Anyone have any clues?