Form does not send POST

Question

I am developing a data import system for XLS to Mysql. The system is practically ready. I did a test with a file xls 24kb and successfully exported without any error. The problem is that I have been testing now with a file xls with 1MB and the error that occurs is that it does not seem to send the POST to the server, which it needs to send for me to upload the file. My maximum limit for sending to the server is 50MB

Form

<form class="form-horizontal" action="" method="post" enctype="multipart/form-data">

  <div class="form-group">
    <label class="col-sm-2 control-label">Banco de dados</label>
    <div class="col-sm-10">
      <input type="file" name="arquivo" class="form-control">
      <small>Envie no formado .xls</small>
    </div>
  </div>
  <div class="line line-dashed b-b line-lg pull-in"></div>

  <div class="form-group">
    <label class="col-sm-2 control-label"></label>
    <div class="col-sm-10">
     <input type="submit" class="btn btn-success" name="submitFile" value="Iniciar Importação">

Upload

if($this->input->post('submitFile')){

    $config['upload_path'] = 'uploads/tmp/';
    $config['allowed_types'] = 'xls|xlsx';
    $config['file_name'] = $this->session->userdata('user_id');
    $config['remove_spaces'] = true;
    $config['overwrite'] = true;

    $this->upload->initialize($config);

    if($this->upload->do_upload('arquivo')){
        redirect('import/database');
    }else{
        redirect('import/upload');
    }

  }