config.phpで次のパラメータを確認してください ファイル。
'baseurlpath' => 'http[s]://YOUR_DOMAIN/simplesaml/',
'session.cookie.domain' => '.YOUR_DOMAIN',
'session.cookie.secure' => true, // ACCORDING TO YOUR REQUIREMENT
'session.phpsession.savepath' => '/PATH/TO/STORE/SESSION', // MAKE SURE THIS PATH IS WRITABLE BY WEB/APP SERVER
'session.phpsession.httponly' => true, // ACCORDING TO YOUR REQUIREMENT