USPS : Ошибка авторизации API

Почему тариф не работает с USPS? Я использую ratev4 и получаю сообщение об ошибке:

Ошибка:

API Authorization failure. RateV4 is not a valid API name for this protocol.
UspsCom::DoAuth

Вот мой код:

<?php
$devurl = "testing.shippingapis.com/ShippingAPITest.dll";
$puburl = "https://secure.shippingapis.com/ShippingAPITest.dll";

$service = "RateV4";
$userid = "690DEVBL1739";

$xml = rawurlencode('<RateV4Request USERID="xxxxx">
    <Revision/>
    <Package ID="1ST">
        <Service>FIRST CLASS</Service>
        <FirstClassMailType>LETTER</FirstClassMailType>
        <ZipOrigination>44106</ZipOrigination>
        <ZipDestination>20770</ZipDestination>
        <Pounds>1</Pounds>
        <Ounces>0.0</Ounces> 
        <Container/>
        <Size>REGULAR</Size> 
        <Machinable>true</Machinable>
    </Package>
    </RateV4Request>');

    $request = $devurl . "?API=" . $service . "&xml=" . $xml;


    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $request);
    curl_setopt($ch, CURLOPT_HEADER, false);
    curl_setopt($ch, CURLOPT_HTTPGET, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);



    $response = curl_exec($ch);
    curl_close($ch);

    echo "<pre>";
    print_r($response);
    echo "</pre>";