title: Merchant Design Identification Error in PayPal Payflow Link
body: <p>My Payflow Link integration has been giving some trouble recently. Whenever I attempt to start a transaction from my web shop, the following error occurs:</p>
  <blockquote>
  <p>Some required information is missing or incorrect. Please correct the fields below and try again.</p>
  <ul>
  <li>Error: Merchant Design Identification Error.</li>
  </ul>
  </blockquote>
  <p>This happens immediately after being transfered to PayPal's hosted payment form. The account I am using is in test mode and the following values are posted to <a href="https://payflowlink.paypal.com/" rel="nofollow noreferrer">https://payflowlink.paypal.com/</a>:</p>
  <pre><code>LOGIN=[login]
  PARTNER=[partner]
  SHOWCONFIRM=true
  ECHODATA=true
  TYPE=S
  AMOUNT=99.99
  INVOICE=123456
  NAME=John Doe
  ADDRESS=Main Street 123
  CITY=Los Angeles
  ZIP=1234
  COUNTRY=US
  PHONE=
  NAMETOSHIP=John Doe
  ADDRESSTOSHIP=Main Street 123
  CITYTOSHIP=Los Angeles
  ZIPTOSHIP=1234
  COUNTRYTOSHIP=US
  PHONETOSHIP=
  </code></pre>
  <p>The <a href="http://www.magentocommerce.com/answers/discussion/471/Error-with-payflow-link/p1" rel="nofollow noreferrer">only result</a> Google has to offer for this error message suggests that the PayPal credentials aren't valid. This doesn't seem to be the case though, because when I send wrong credentials, I get a different error message, not this one. Also, I can log into PayPal Manager using these credentials and it doesn't report a 'deactivated account' status anywhere.</p>
  <p>Has anyone else encountered this error message? And, more importantly, how do I fix it?</p>