Use a fresh site without any course custom fields Enable global search (Admin > Advanced features) Go to Site administration > Plugins > Search > Search areas and disable all areas but "Course custom fields" to make indexing faster. Install tool_certificate ( https://moodle.org/plugins/tool_certificate ) and mod_coursecertificate ( https://moodle.org/plugins/mod_coursecertificate ) plugins (for Moodle 3.8 you will need to modify the required moodle version in the version.php) Create a new course and enrol a student to it Add a new Course certificate instance to the course, with default demo template and no access restriction Log in as the student Visit the certificate module page to get the certificate issued. As admin, run the scheduled task core\task\search_index_task via the command line: php admin/cli/scheduled_task.php --execute= "\core\task\search_index_task" TEST Make sure the task finishes succesfully and you do not see "Exception - Call to a member function get() on null"