CI 3.0 is losing Session always

Hello, I have started a web site with CI 3.0, but I am with a problem with storing session.

I create the session example:

PHP Code:

$newdata = array(
        'username'  => 'johndoe',
        'email'     => '[email protected]',
        'logged_in' => TRUE
);

$this->session->set_userdata($newdata); 


But in refresh, every sessions has removed.

My config:

PHP Code:

$config['sess_driver'] = 'database';
$config['sess_cookie_name'] = 'ci_session';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = 'ci_sessions';
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 300; 


My autoload

PHP Code:

$autoload['libraries'] = array('database', 'session');
$autoload['drivers'] = array('session');