Calendar App for Office 365
To overlay Calendars from different Site Collections and (or) Calendars, Meeting Rooms from Exchange Online, you need to register Calendar Authorization App...
Thu, Aug 23, 2018 at 7:27 AM
We have created an App with same ID that you can install in your tenant App Catalog. https://download.virtosoftware.com/dev/Calendar_ProviderHosted.app
Thu, Aug 23, 2018 at 7:28 AM