Form validation required not firing

You need to read the tutorial again, now you got two RUN() functions.
Start fresh and just copy that code before you try to introduce your code.

same, I introduced a single function, but it still does not block when the fields are empty

Code:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Login_controller extends CI_Controller {

    public function index()
    {
        echo 'welcome to login';
    }

    function login_pro()
    {
        /*echo $user = $this->input->post('user');
        echo $pass = $this->input->post('pass');*/

        $this->form_validation->set_rules('Username','Username','required');
       
        $this->form_validation->set_rules('Password','Password','required');

          if ($this->form_validation->run() == FALSE)
               {
                       echo 'try again';
               }
               else
               {
                       echo 'welcome';
               }
    }
}