I get this error:
Fatal error: Call to undefined function get_option() in /testserver/wordpress/wp-content/plugins/event-registration/event_registration_export.php on line 24
The reason you are getting that error is that wordpress is not installed in the root directory of your website. The plugin was written assuming it would be in the root installation. In the plugin folder there is a file called event_registration export.php you will need to change line 3.
Current:
3. define( ‘ABSPATH’, $_SERVER['DOCUMENT_ROOT'] . ‘/’ );
Modified:
3. define( ‘ABSPATH’, $_SERVER['DOCUMENT_ROOT'] . ‘/your_subdirectory_name