Problem with mobile-only Ajax request

Question

I have a code Ajax that takes the data from a simple message field and sends it to my database without the page being updated, only the problem is that everything works perfectly only by computer, when access by mobile phone the sending simply does not happen.

HTML:

<form method="post" action="../controller/SendChatMessage.class.php?act=open_chat&id_unique_talk=<?=$get_id_unique_talk?>&to_id=<?=$get_id_para?>" id="send_message_chat" ajax="true">
      <div class="col-sm-10">
         <div class="message-area">
            <textarea placeholder="Message" rows="10" name="message" id="txt_message"></textarea>
         </div>
      </div>
      <button style="height:28px;margin-top:-39px !important;" type="submit" class="btn btn-primary pull-right"> <i class="fa fa-send"></i></button>
 </form>

Javascript:

<script type="text/javascript">
$(document).ready(function(e) {

  $("form[ajax=true]").submit(function(e) {

      e.preventDefault();

      var form_data = $(this).serialize();
      var form_url = $(this).attr("action");
      var form_method = $(this).attr("method").toUpperCase();

      $("#loading").show();

      $.ajax({
          url: form_url, 
          type: form_method,      
          data: form_data,     
          cache: false,
          success: function(returnhtml){                          
              $("#result").html(returnhtml); 
              $("#loading").hide();
              document.getElementById('txt_message').value='';
          }           
      });    

  });

});
</script>

I wonder if someone could help me?