Why doesn't sending data from the form to Ajax work in the Instagram browser?

Question

AJAX

Hello. There is such a project https://maria-psy.ru/robot-copy/index.html . To start a session, you need to fill out the form. Sending data is implemented using Ajax. Here is the piece of code that is responsible for this

$(function(Subscribe) {
  $('.uni-form').submit(function(e) {
    var $form = $(this);
    $.ajax({
      type: $form.attr('method'),
      url: $form.attr('action'),
      data: $form.serialize()
    }).success(function(){
      console.log('success');
      setCookie('subscribed', 'true', 365, false);
      $('.popup').removeClass('d-flex').addClass('d-none');
      startConsultation();
    }).fail(function() {
      console.log('fail');
    });
    //отмена действия по умолчанию для кнопки submit
    e.preventDefault(); 
  });
  console.log(document.cookie);
});

It works fine in all browsers, except for the built-in Instagram browser. Tell me, please, what's wrong?
And how to understand what is happening in this browser. Is there an insta browser tool like Chrome DevTools?