microsoft graph api calendar access denied

Question

my application has an events feature that should get updated for all the attendees when the event is edited. i can see that the cupdate works for my calender but does not update for other attendees. i get a Access denied error. The application has Calendars.ReadWrite access.

error="DelegatedCalendarAcessDenied"
message=Access is denied. Check credential and Try again"

i am using
.api("users/${userprincipalName}/calendar/events/{id}");

any insights would be helpful.
does the user updating the change need an admin account to make sure he has access to everyone's calendar?

Answer 1

You must be using only delegated permissions to call users/{id}/calendars/events/{id}. You get access denied because for your user-id, delegated permissions apply but for other users calendars, you need application permissions.

You need to add Calendars.ReadWrite Application Permission not Delegated Permissions to your app and try again.