Gianism requires session and some server doesn’t provide it.

Gianism requires session.

It’s normal to use session for persistent user recognition because PHP supports session by default.

But WordPress doesn’t use session for user-login but cookie. It’s O.K. itself, but as a result some hosting providers(especially WordPress hosting) don’t provide it.

For example, the error which this forum question mentioned is caused by KUSANAGI‘s setting.

So, turn session on. That’s it.

How to check if session works

To check if session works on PHP, upload a script session.php on your server. If session works, every time you access via browser the number will be increased. If  not, session doesn’t work.

<?php
session_start();

if ( ! isset( $_SESSION['number'] ) ) {
    $_SESSION['number'] = 0;
}
$_SESSION['number']++;
echo $_SESSION['number'];

On local environment like MAMP or XAMPP, session might be turned off by default. You can solve it by googling “XAMPP session”.

On productional environment, you might use some hosting provider. Ask them what to do.

How about multiple servers environment?

I know some huge site which consists of multiple servers environment. In such situation, session becomes very sensitive matter, because normal session saves cache files on its own directory.