isConnected always returns false? HabboPHP

[Thewicard]

    public function isConnected(){
        if(isset($_SESSION['Auth']) && $_SESSION['Auth'] == true && isset($_COOKIE['Auth']) && $_SESSION['Timeout'])
        {
            $sql = mysql_query('SELECT id FROM users WHERE id='.safe($this->uid,'SQL'));
            if(mysql_num_rows($sql) == 1)
            {
                if($_COOKIE['Auth'] == $this->getSaltUsers($this->uid))
                {
                    $this->setLast_online($this->uid);
                    $this->setIP_last($this->uid);
                    return true ;
                }
            }
        }
        return false ;
                            
    } 

This code always returns with false when using Cloudflare, or other TCP Proxy.
Any reason?

[MentaL]