To trigger learndash notifications, one must use a cron alike mechanism
Basically (http) requesting regularly an url: https://<your-wordpress-website>/wp-cron.php?doing_wp_cron&cron=true
So one could use wget or curl in the cron job.
It’s ok this returns a white screen as you use this in a browser. A process in the background will be started.
GOAL: The cron will check a specific table to determine whethere emails should be send out right now.


The table below is used to store emails that should be send out on a later timestamp.

SELECT * FROM <you_database>_ld_notifications_delayed_emails

You’ll see it gets populated e.g. if you have notifications defined when a user is added to a course and you add a new user to a course. The notifications that should send out immediately will not land in that table.


To view logging for learndash notifications one can consult the log file:
https://<your-wordpress-website>/wp-content/uploads/learndash/learndash-notifications-actions.log
If that does not work, one can use FTP to go to the file above.

One will see log data as below.
It can give you insight into what notifications are being scheduled, which are not.

[2020-12-29 08:16:23]: Notification with these data: {"user_id":7,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":110,"group_id":null,"quiz_result":[]} was sent.
[2020-12-29 11:01:08]: Notification with these data: {"user_id":9,"course_id":189,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":194,"group_id":null,"quiz_result":[]} was sent.
[2020-12-29 11:01:08]: Scheduled notification for the timestamp: 1609326068 with these data: a:10:{s:7:"user_id";i:9;s:9:"course_id";i:189;s:9:"lesson_id";i:192;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:196;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2020-12-29 11:07:00]: Notification with these data: {"user_id":10,"course_id":189,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":194,"group_id":null,"quiz_result":[]} was sent.
[2020-12-29 11:07:00]: Scheduled notification for the timestamp: 1609326420 with these data: a:10:{s:7:"user_id";i:10;s:9:"course_id";i:189;s:9:"lesson_id";i:192;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:196;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2020-12-29 11:59:53]: Scheduled notification with these data: {"notification_id":196,"user_id":"10","course_id":"189","lesson_id":"192"} was updated in database with these new data: a:10:{s:7:"user_id";s:2:"10";s:9:"course_id";s:3:"189";s:9:"lesson_id";s:3:"192";s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:196;s:8:"group_id";N;s:11:"quiz_result";a:0:{}}. 1 row was affected.
[2020-12-30 12:43:33]: Scheduled notification with these data: {"user_id":"10","course_id":"189","lesson_id":"192","topic_id":"","assignment_id":"","quiz_id":"","question_id":"","notification_id":196,"group_id":"","quiz_result":""} was sent.
[2021-01-04 08:45:01]: Notification with these data: {"user_id":13,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-04 09:03:06]: Notification with these data: {"user_id":14,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-04 09:15:15]: Notification with these data: {"user_id":15,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-04 09:27:43]: Notification with these data: {"user_id":16,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-04 10:28:23]: Notification with these data: {"user_id":17,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-05 15:48:23]: Notification with these data: {"user_id":18,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-07 11:07:34]: Notification with these data: {"user_id":19,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-08 06:22:21]: Notification with these data: {"user_id":20,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-08 08:04:48]: Notification with these data: {"user_id":21,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-08 09:08:51]: Notification with these data: {"user_id":22,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-08 09:38:24]: Notification with these data: {"user_id":23,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-08 11:34:23]: Notification with these data: {"user_id":24,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-13 11:17:19]: Notification with these data: {"user_id":25,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-13 12:59:46]: Notification with these data: {"user_id":26,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-13 18:27:27]: Notification with these data: {"user_id":27,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-13 18:31:01]: Notification with these data: {"user_id":28,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-15 16:29:48]: Notification with these data: {"user_id":29,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-17 22:14:30]: Notification with these data: {"user_id":30,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-18 17:23:39]: Scheduled notification for the timestamp: 1612200219 with these data: a:10:{s:7:"user_id";i:31;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1032;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-01-18 17:23:39]: Scheduled notification for the timestamp: 1611595419 with these data: a:10:{s:7:"user_id";i:31;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1028;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-01-18 17:23:39]: Notification with these data: {"user_id":31,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-01-25 17:30:10]: Scheduled notification with these data: {"user_id":31,"course_id":20,"lesson_id":"","topic_id":"","assignment_id":"","quiz_id":"","question_id":"","notification_id":1028,"group_id":"","quiz_result":""} was sent.
[2021-02-01 17:30:08]: Scheduled notification with these data: {"user_id":31,"course_id":20,"lesson_id":"","topic_id":"","assignment_id":"","quiz_id":"","question_id":"","notification_id":1032,"group_id":"","quiz_result":""} was sent.
[2021-02-07 11:02:08]: Scheduled notification for the timestamp: 1613905328 with these data: a:10:{s:7:"user_id";i:32;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1032;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-07 11:02:08]: Scheduled notification for the timestamp: 1613300528 with these data: a:10:{s:7:"user_id";i:32;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1028;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-07 11:02:08]: Notification with these data: {"user_id":32,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-02-14 11:30:07]: Scheduled notification with these data: {"user_id":32,"course_id":20,"lesson_id":"","topic_id":"","assignment_id":"","quiz_id":"","question_id":"","notification_id":1028,"group_id":"","quiz_result":""} was sent.
[2021-02-15 21:05:34]: Scheduled notification for the timestamp: 1617051934 with these data: a:10:{s:7:"user_id";i:33;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1236;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-15 21:05:34]: Scheduled notification for the timestamp: 1616447134 with these data: a:10:{s:7:"user_id";i:33;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1233;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-15 21:05:34]: Scheduled notification for the timestamp: 1615842334 with these data: a:10:{s:7:"user_id";i:33;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1232;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-15 21:05:34]: Scheduled notification for the timestamp: 1615237534 with these data: a:10:{s:7:"user_id";i:33;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1231;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-15 21:05:34]: Scheduled notification for the timestamp: 1614632734 with these data: a:10:{s:7:"user_id";i:33;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1032;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-15 21:05:34]: Scheduled notification for the timestamp: 1614027934 with these data: a:10:{s:7:"user_id";i:33;s:9:"course_id";i:20;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1028;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-15 21:05:34]: Notification with these data: {"user_id":33,"course_id":20,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":381,"group_id":null,"quiz_result":[]} was sent.
[2021-02-17 09:30:30]: Notification with these data: {"user_id":18,"course_id":189,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":1346,"group_id":null,"quiz_result":[]} was sent.
[2021-02-17 09:34:01]: Scheduled notification for the timestamp: 1613640841 with these data: a:10:{s:7:"user_id";i:34;s:9:"course_id";i:189;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1349;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-17 09:34:03]: Notification with these data: {"user_id":34,"course_id":189,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":1346,"group_id":null,"quiz_result":[]} was sent.
[2021-02-26 10:51:04]: Scheduled notification for the timestamp: 1614423064 with these data: a:10:{s:7:"user_id";i:35;s:9:"course_id";i:189;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1349;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-26 10:51:05]: Notification with these data: {"user_id":35,"course_id":189,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":1346,"group_id":null,"quiz_result":[]} was sent.
[2021-02-26 10:58:01]: Scheduled notification for the timestamp: 1614423481 with these data: a:10:{s:7:"user_id";i:36;s:9:"course_id";i:189;s:9:"lesson_id";N;s:8:"topic_id";N;s:13:"assignment_id";N;s:7:"quiz_id";N;s:11:"question_id";N;s:15:"notification_id";i:1349;s:8:"group_id";N;s:11:"quiz_result";a:0:{}} was stored in database.
[2021-02-26 10:58:01]: Notification with these data: {"user_id":36,"course_id":189,"lesson_id":null,"topic_id":null,"assignment_id":null,"quiz_id":null,"question_id":null,"notification_id":1346,"group_id":null,"quiz_result":[]} was sent.