Checkbox Validation using a hidden field with jquery validate

Question

I have multiple checkbox inputs that I am trying to create validation for. At least one checkbox has to be selected for the form to submit. What I did was add a hidden input. Then with a change function, there is a join function that combines the checkbox values. Under that there is a variable that checks for the checkboxes' length.

In the jQuery validate, I have tried requiring the field and the parent radio button that produces its associated checkboxes. Then the checkbox fields I have set a min of 1.

Currently, when I hit submit, the form goes through without any of the checkboxes being selected or the parent radio buttons.

Does anyone see what I am doing wrong?

$(document).ready(function() {
  var showMe = '';
  /*var checkLength = '';
  $('#interest').val(checkLength);
  console.log(checkLength);*/
  var newStatus = '';
  //Telling whether new is selected
  var usedStatus = '';
  //Telling whether used is selected
  var newSelPush = '';
  var usedSelPush = '';
  $('.equipmentOptionCont').change(function() {
    var newSel = [];
    var usedSel = [];
    //Get new mower options 
    $("input:checkbox[name=newMowerOption]:checked").each(function() {
      newSel.push($(this).val());
      newSelPush = newSel.join(', ');
    });
    //Get used mower options
    $("input:checkbox[name=usedMowerOption]:checked").each(function() {
      usedSel.push($(this).val());
      usedSelPush = usedSel.join(', ');
    });

    //Interest length creation for validation
    var interestCheck = (newSelPush || usedSelPush);
    //Hidden interest input value
    checkLength = interestCheck.length;
    console.log(checkLength);
    $('[name="interestHidden"]').val(checkLength);

  });

  //Validation

  $('#prodNotifForm').validate({
    onfocusout: true,
    rules: {
      interestHidden: {
        //required: true,
        required: $('#newMowerSelect').prop('checked') == true,
        min: 1
      }
    },
    messages: {
      interestHidden: {
        required: "Please choose at least one interest",
        min: "At least one interest needs chosen"
      }
    },
    errorPlacement: function(error, element) {
      if ($(element).attr('name') == 'interestHidden') {
        error.insertBefore(element.parent('div'));
      } else {
        error.insertAfter(element); // <- default
      }
    },
    submitHandler: function(form) {
      //Variables for the form ids
      var notifFirstName = $('#notifFirstName').val();

      $.ajax({
        url: 'subscriberNotifSend.php',
        type: 'POST',
        data: {
          'notif_first_name': notifFirstName,

        },
        success: function(data) {
          //console.log(data); // data object will return the response when status code is 
        },
        complete: function() {

        },
        error: function(xhr, textStatus, errorThrown) {
          alert(textStatus + '|' + errorThrown);
          //console.log('error'); //otherwise error if status code is other than 200.
        }
      });
    }
  });

});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.19.1/jquery.validate.js"></script>
<form id="prodNotifForm">
  <div id="interestContainer">
    <input type="radio" name="notifymethod" id="newMowerSelect" class="equipmentMainSel notifCheck">
    <label for="newMowerSelect" class="checkMower">
         <div class="labelMowerSelect">New</div>
         <img src="" alt="New Mower Options" class="mowerOptionImgs">
        </label>
    <input type="radio" name="notifymethod" id="usedMowerSelect" class="equipmentMainSel notifCheck">
    <label for="usedMowerSelect" class="checkMower">
         <div class="labelMowerSelect">Used</div>
         <img src="" alt="Used Mower Options" class="mowerOptionImgs">
        </label>
    <div id="interestError"></div>
    <div id="newMowerOptions" class="equipmentOptionCont">
      <p class="notifQuestion">New Mower Options</p>
      <div class="equipmentWrap">
        <label class="equipmentOptions">Ferris</label>
        <input type="checkbox" name="newMowerOption" value="Ferris">
      </div>
    </div>
    <div id="usedMowerOptions" class="equipmentOptionCont">
      <p class="notifQuestion">Used Mower Options</p>
      <div class="equipmentWrap">
        <label class="equipmentOptions">Ferris</label>
        <input type="checkbox" name="usedMowerOption" value="Ferris">
      </div>
    </div>
    <div><input type="hidden" id="interestHidden" name="interestHidden" value=""></div>
  </div>
  <button id="notifSubmit">Sign up</button>
</form>