A calendar shared with you in the new approach appears as just another calendar in your mailbox.You can use the calendar REST API to view or edit events in the shared calendar, as if it's your own calendar.If you accept or decline a meeting by using the meeting item in the Calendar in Outlook, the meeting request remains in the Inbox.
Many people assume that the Office 365 calendar system tracks a meeting as a single copy and that any edits to a meeting will automatically update and appear for all attendees.
Instead, in order to allow Office 365 meetings to work with other calendaring systems and external users, all calendaring data requires the sending and receiving of email messages to all attendees.
Mobile devices tend to cause the most issues with appointments becoming corrupt, missing, or out of sync.
Scheduling an appointment just for yourself on your mobile device is ok.
Keep current with Microsoft Office Updates - There are known issues that are fixed with each service pack or update.
Make sure your mobile device has the latest OS/i OS version.If a calendar was shared with view or edit permissions but using the old approach, you can now work around the error and manually upgrade the calendar sharing to use the new approach.Over time, Outlook will automatically upgrade all shared calendars to use the new approach, including calendars shared with delegate permissions.Microsoft has documented this in their Known Issues release. The Greenhouse integration relies on Outlook365’s calendar REST API, which can only be used to access shared calendars using the “new” approach.The owner of the calendar should right-click on the calendar to open the Sharing Permissions (for a shared mailbox, a user with access to manage the mailbox’s sharing permissions must open the shared mailbox directly).Depending on the level of access they've granted you, you may also be able to modify items.