Embed form prefill

Hi!
I'm working with one of our developers to implement @SanfordWhiteman 's prefill solution and we've run into an issue. The developer does not have access to Community so I'm posting as a proxy. Any help would be appreciated!

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I followed the instructions closely from the post and am using the updated SimpleDTO2, but have been running into issues. 

I set up a Guided Landing page and have the associated DTO with the configured html. However, when I open a Marketo form from the destination site I receive the following error: “Message receive preflight failed, origin: uat.example.com and pages.e.example.com cannot exchange messages. I realize this is a CORS error but if I visit pages.e.example.com directly it re-routes me to another page, so I am unable to set the Headers on that page to allow the origin request.   (pages.e.example.com is the Marketo landing page CNAME)

Following the instructions in the blog post, I would not expect a CORs error to be occurring. I was hoping you might have an on what I could be doing wrong or potential workarounds I could try? I am not able to create a proxy server to get around CORs. 

The configuration I have on my receiving site is below (the teknkl-formsplus-core-1.0.8.js and teknkl-simpledto-2.0.4.js script files both are set in a CDN and appear to be loading correctly):

  const DTO = new SimpleDTO({
          debug: true,
          mode: 'receive',
          transport: 'message',
          messageSource: 'https://pages.e.example.com',
          messageTarget: ['https://uat.example.com'],
          dataSrc: 'https://pages.e.example.com/dtp-104.html',
          cb: function (instance: any, mktoFields: any) {
            MktoForms2.whenReady(function (form: { setValuesCoerced: (arg0: any) => void }) {
              form.setValuesCoerced(mktoFields);
            });
            DTO.cleanup();
          },
        });
 
And then in my Marketo instance I have:
 
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>DTP</title>
    <script
      id="teknkl-FormsPlus-Core-1.x"
      src=“https://path_to_CDN_stored/teknkl-formsplus-core-1.0.8.js"
    ></script>
    <script
      id="teknkl-SimpleDTO-2.x"
      src=“https://path_to_CDN_stored/teknkl-simpledto-2.0.4.js"
    ></script>
    <script
      type="text/xml"
      class="dto-xml"
      data-field-collection="mktoPreFillFields_01"
    >
      <mktoPreFillFields>
       <mktoField inputName="FirstName">{{Lead.First Name}}</mktoField>
       <mktoField inputName="LastName">{{Lead.Last Name}}</mktoField>
       <mktoField inputName="Email"><!--email_off-->{{Lead.Email Address}}<!--/email_off--></mktoField>
       <mktoField inputName="Country">{{Lead.Country}}</mktoField>
       <mktoField inputName="State">{{Lead.State}}</mktoField>
       <mktoField inputName="Title">{{Lead.Job Title}}</mktoField>
       <mktoField inputName="Industry">{{Company.Industry}}</mktoField>
       <mktoField inputName="Company">{{Company.Company Name}}</mktoField>
       <mktoField inputName="Company">{{Lead.Marketing Consent Date}}</mktoField>
       <mktoField inputName="Company">{{Lead.Marketing Consent Reason}}</mktoField>
      </mktoPreFillFields>
    </script>
    <script>
      var DTO = new SimpleDTO({
        debug: true,
        mode: "send",
        transport: "message",
        messageSource: " https://pages.e.example.com",
        messageTarget: ["https://uat.example.com"],
        dataSrc: "https://pages.e.example.com/dtp-104.html",
      });
      DTO.parse("mktoPreFillFields_01");
    </script>
  </head>
  <body></body>
</html>