Form does not send POST

I'm developing an XLS for MySQL data import system. The system is practically ready. I ran a test with a xls 24kb file and successfully exported without any errors. The problem is that I was testing now with a xls file with 1MB and the error that occurs is that it seems that it does not send the POST to the server, and that it needs to be sent to me to upload the file. My maximum upload limit on 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');
    }

  }