phpGrid requies session to work.
First of all, if you have access to php.ini, check if path in session.save_path is valid and writable. In Linux, by default, the path is /var/php_sessions/
In addition, please make sure session.auto_start must be set to 1 in php.ini.
Some web hosting services such as iPage, disallows shared user session folder for security reasons. Users MUST create and maintain their own session folder.