Is this issue sorted out now? I’m facing the same issue as mentioned in the description. (calendar shows the first event only when it was opened from outlook client, and it shows all the events when it opened from outlook browser)
#You can Import an ICS file into within Outlook for Office 365:
Click File – Open & Export – Import/Export
Choose Import an iCalendar (ics) or vCalendar file (vcs) > Next
Browse to the path containing your ICS File
Select the file and click import
Now check your outlook calendar.
With METHOD:PUBLISH, you can add multiple events and upon opening the iCal with MS Outlook it will create a new calendar, separate from your main Exchange calendar. The METHOD:REQUEST creates a calendar invite, so you can only include one event and upon opening with MS Outlook. It will ask you to accept the event and add it to your main Exchange calendar. Please check the following code snippet. Hope this helps you.
IcsSaveOptions saveOptions = new IcsSaveOptions();
saveOptions.setAction(AppointmentAction.Create);
saveOptions.setMethodType(AppointmentMethodType.Publish);
CalendarWriter writer = new CalendarWriter("WriteMultipleEventsToICS_out.ics", saveOptions);