When trying to access a user calendar (one created especially for the purpose, not their main one) through the Graph API, I get a 404.
"/users/$email/calendars/$calendar_id"
The calendar exists because it can be seen in the Outlook web app.
Since the calendar exists to receive automated data from a custom CRM I can get out admin to delete it, I can then successfully create it again, store the ID.
Then receive another 404 seconds after creation. Still getting a 404 an hour later. This is an ongoing problem that has been occurring for months, it just took a while to figure out how to test it; so it seems unlikely to be a Microsoft Server issue.
There are 18 other users that this works fine for; our admin say they cannot find any configuration differences with the problem user's account; and it seems unlikely the user in question is doing anything to interfere given the small timescales.
This is the only user to have any iOS devices, but that feels like its probably be a coincidence
