I've created the following iCalendar file to generate the initial event
BEGIN:VCALENDAR
VERSION:2.0
PRODID:icalendar-ruby
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20170529T184713Z
UID:call_286@foobar.dev
DTSTART:20170427T160000Z
DTEND:20170427T163000Z
DESCRIPTION:A test call
SEQUENCE:7
STATUS:CONFIRMED
SUMMARY:A test call
URL:http://foobar.dev/calls/286
BEGIN:VALARM
ACTION:DISPLAY
TRIGGER:-PT15M
DESCRIPTION:Starting in 15 minutes - A test call
SUMMARY:A test call starting in 15 minutes
END:VALARM
END:VEVENT
END:VCALENDAR
This event is properly imported into OSX's Calendar (v 9.0) with all the correct details and Sync'd to Google Calendar.
I then update the event and generate an updated iCalendar file, keeping the UID
the same and increment the SEQUENCE
as per the specification
BEGIN:VCALENDAR
VERSION:2.0
PRODID:icalendar-ruby
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20170529T185549Z
UID:call_286@foobar.dev
DTSTART:20170427T153000Z
DTEND:20170427T155500Z
DESCRIPTION:A test call
SEQUENCE:8
STATUS:CONFIRMED
SUMMARY:A test call
URL:http://foobar.dev/calls/286
BEGIN:VALARM
ACTION:DISPLAY
TRIGGER:-PT15M
DESCRIPTION:Starting in 15 minutes - A test call
SUMMARY:A test call starting in 15 minutes
END:VALARM
END:VEVENT
END:VCALENDAR
I then import this event into OSX's Calendar and my original event disappears from the calendar completely. It doesn't update at all just completely disappears.
When I look at Google Calendar the original event is still there in the exactly the same place as per the initial time schedule.
What am I doing wrong that the event is not updating?
Update: This question is not a duplicate of Update an event in Outlook 2007 with an iCalendar file or ICalendar and event updates not working in Outlook or Update an event in Outlook 2007 with an iCalendar file as this question related to OSX's Calendar (v 9.0) application and subsequent syncing with Google Calendar and not Outlook. I have tried the approaches described in answers to those questions but I get exactly the same behaviour as described above.