jQuery: Weird issue with .on('click')

Hello, all,

I've got a weird issue with a jQuery .on('click') call.  It won't even trigger an alert.  The following is part of a Bootstrap v4 modal.

<button class="btn btn-primary" id="submitBtn" name="submitBtn">Submit</button>
<button class="btn btn-secondary" id="closeBtn" name="closeBtn">Close</button>
<!-- Here is where I'm loading jQuery, Bootstrap, and popper.js -->
<script type="text/javascript">
     $('#submitBtn').on('click',function(){
          alert("I have been clicked.");
          });
</script>

When I open the modal and click the submit button, I get no alert.  jQuery is loading properly.  Nothing is appearing in the error console.  Any thoughts?

V/r,

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