No notifications sent, parseCalendarData() must be of the type string, null given

Nextcloud version: 19.0.2
Operating system and version: Ubuntu 20.04
Apache or nginx version: Apache
PHP version: 7.4

The issue you are facing:
No email notifications sent for calendar events.
Log shows:
OCA\DAV\CalDAV\Reminder\ReminderService::parseCalendarData() must be of the type string, null given

Is this the first time you’ve seen this error?: Y

Steps to replicate it:

  1. Create calendar event.
  2. Set notification

The output of your Nextcloud log in Admin > Logging:

{"reqId":"frXoJrfniSRI5B9ItNdy","level":3,"time":"2020-09-08T22:00:05+00:00","remoteAddr":"","user":"--","app":"core","method":"","url":"--","message":{"Exception":"TypeError","Message":"Argument 1 passed to OCA\\DAV\\CalDAV\\Reminder\\ReminderService::parseCalendarData() must be of the type string, null given, called in /var/www/nextcloud/apps/dav/lib/CalDAV/Reminder/ReminderService.php on line 120","Code":0,"Trace":[{"file":"/var/www/nextcloud/apps/dav/lib/CalDAV/Reminder/ReminderService.php","line":120,"function":"parseCalendarData","class":"OCA\\DAV\\CalDAV\\Reminder\\ReminderService","type":"->"},{"file":"/var/www/nextcloud/apps/dav/lib/BackgroundJob/EventReminderJob.php","line":68,"function":"processReminders","class":"OCA\\DAV\\CalDAV\\Reminder\\ReminderService","type":"->"},{"file":"/var/www/nextcloud/lib/private/BackgroundJob/Job.php","line":62,"function":"run","class":"OCA\\DAV\\BackgroundJob\\EventReminderJob","type":"->"},{"file":"/var/www/nextcloud/lib/private/BackgroundJob/TimedJob.php","line":57,"function":"execute","class":"OC\\BackgroundJob\\Job","type":"->"},{"file":"/var/www/nextcloud/cron.php","line":126,"function":"execute","class":"OC\\BackgroundJob\\TimedJob","type":"->"}],"File":"/var/www/nextcloud/apps/dav/lib/CalDAV/Reminder/ReminderService.php","Line":677,"CustomMessage":"Error while running background job (class: OCA\\DAV\\BackgroundJob\\EventReminderJob, arguments: )"},"userAgent":"--","version":"","id":"5f57ffd9a92d2"}

select * from oc_calendarobjects where calendardata is null; returns 0 rows.

I imported a couple of Google Calendars when I started with NC and have the issue that no notifications are sent via mail at all.
When exporting the calendars from NC it looks like the old Google Calendars may contain some characters that NC might be tripping about.

Any ideas on how to further troubleshoot that would be appreciated.

I have now even validated all my calendars and removed all subscribed calendars that showed errors.
So all my current calendars pass the validator on without errors, however the issue still remains.

Nothing at all?
Not even a hint at what to troubleshoot?

I experience exactly the same issue. Am on NC 20.0.1 with Calendar app 2.1.2.

Argument 1 passed to OCA\\DAV\\CalDAV\\Reminder\\ReminderService::parseCalendarData() must be of the type string, null given, called in /var/www/nextcloud/apps/dav/lib/CalDAV/Reminder/ReminderService.php on line 120

Any tips on troubleshooting is appreciated.

Although just a minor thing, it was still bothering me, so I gave it another go.

Found the solution to my problem here:

There was one entry in oc_calendar_reminders which apparently was causing the issue. Deleted the reminder (delete from oc_calendar_reminders where event_hash=‘xxxxxxx’:wink: and the errors in the Nextcloud log were not generated anymore.