Fatal error: Uncaught Error: Interface "Concrete\Core\Notification\Subject\SubjectInterface" not found in /srv/disk1/2895578/www/whittonphotographicclub.org.uk/concrete/src/Entity/User/UserSignup.php:16 Stack trace: #0 {main} thrown in /srv/disk1/2895578/www/whittonphotographicclub.org.uk/concrete/src/Entity/User/UserSignup.php on line 16