Form validation required not firing

I've already done that,  but without success

OK!
I've taken the code you have pasted in and created a brand new installation of CI 3.1.8

In order to get this thing working i had to do 2 changes to your code:

1, in the form i've changed base_url() to site_url()
2, see the example class

PHP Code:

<?php
class Test extends CI_Controller {

    public function __construct() {
        parent::__construct();
        // Loading helpers and library
        $this->load->helper(array('form', 'url'));
        $this->load->library('form_validation');
    }

    function login_pro() {

        $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';
        }
    }

} 


Now, this is working fine on linux on PHP 7.2.5

Personally i do not like the case sensitive name tags in the form, so if it would be up to me u would rename Username to username, but that is just my preference..

hello,

I did what you suggested, but it still does not work.