Blocking Spam & Personal Domains Issue

Hi! I'm trying to us @SanfordWhiteman's script to block personal and spam domains but for some reason when I add the script to my Marketo landing page HTML, it just redirects back to the page once clicking submit versus giving the "Must be business email" validation rule.

Here's the landing page: https://it.recastsoftware.com/automatedpatching.html

I did remove the script as the page is live and I couldn't get the redirect to stop but this is what code I dropped in before the </body> tag.

<!-- FormsPlus libraries -->
<script id="teknklFormsPlus-EmailPattern-1.0.3" src="https://it.recastsoftware.com/rs/563-ODB-688/images/teknkl-formsplus-emailpattern-1.0.3.js?version=0"></script>
<!-- /FormsPlus libraries -->

And here's the modified JS:

/*
 * @author Sanford Whiteman
 * @version v1.1 2020-11-15
 * @copyright © 2020 Sanford Whiteman
 * @license Hippocratic 2.1: This license must appear with all reproductions of this software.
 *
 *
 *
 */

(function () {
   const invalidDomains = [
      "gmail.com", 
      "yahoo.com", 
      "hotmail.com",
      "sandy@fig1.com",
      "jourrapide.com",
      "teleworm.us",
      "armyspy.com",
      "rhyta.com",
      "cuvox.de",
      "dayrep.com",
      "einrot.com",
      "fleckens.hu",
      "gustr.com",
      "superrito.com",
      "sandy@fig1.net"
      ]
      invalidMessage = "Must be a Business email.";

   const interestingEmailField = "Email";

   /* NO NEED TO ALTER BELOW THIS LINE */

   MktoForms2.whenReady(function (mktoForm) {
      const formEl = mktoForm.getFormElem()[0],
         emailEl = formEl.querySelector("[name='" + interestingEmailField + "']");

      mktoForm.onValidate(extendedEmailValidation);

      function extendedEmailValidation(nativeValid) {
         if (nativeValid === false) return;

         let currentValues = mktoForm.getValues(),
            originalSubmittable = mktoForm.submittable(),
            email = currentValues[interestingEmailField];

         if (email) {
            if (FormsPlus.emailPattern.match(email, invalidDomains)) {
               console.log("Email matches pattern, forcing submittable(false)");
               emailEl.classList.add("customInvalid");
               emailEl.setAttribute("aria-invalid", "true");
               mktoForm.submittable(false);
               mktoForm.showErrorMessage(invalidMessage, MktoForms2.$(emailEl));
            } else {
               console.log("Email does not match pattern, continuing");
               emailEl.classList.remove("customInvalid");
               emailEl.setAttribute("aria-invalid", "false");
               mktoForm.submittable(originalSubmittable);
            }
         }
      }
   });
   
})();