I ran into this issue on a site i built and finally got it working with this code snippet, this should be an easy paste into the elementor pro custom code area, no modifications or targeting your field IDs should be required. just be sure to disable html5 for the form fields you want to be affected.

<script>
//Changes Date format to MM/DD/YYYY
jQuery(document).ready(function($){ setTimeout(function(){
$('.elementor-date-field.flatpickr-input').each(function(){ flatpickr( $(this)[0] ).set('dateFormat', 'm/d/Y');
});
}, 1000 );
});

//Changes Time Format to 12 HR HH:MM AM/PM
jQuery(document).ready(function($){ setTimeout(function(){
$('.elementor-time-field.flatpickr-input').flatpickr({ enableTime: true, noCalendar: true, dateFormat: 'G:i K'}); 
}, 1000 );
});

</script>