Unable to sync Calendar with macOS Calendar Application

calendar
9.1.x
help

#1

Steps to reproduce
1. Add the calendar extension to ownCloud
2. Create a calendar, and copy the appropriate URL
3. Try to add the calendar to the Calendar app on MacOS Sierra
4. Receive the following error message;

The data downloaded from http://owncloudserver.com/remote.php/dav/calendars/username/calendarname/ isn’t valid.

Expected behaviour
Tell us what should happen

Actual behaviour
Tell us what happens instead

Server configuration
Operating system: CentOS 7
Web server: Apache
Database: MariaDB
PHP version: 5.6
ownCloud version (see ownCloud admin page): 9
Updated from an older ownCloud or fresh install: fresh install
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption): data stored on nfs share (hosted on a NAS on the same network)

Integrity status for oC9+

No errors have been found.