Currently, subscribed Exchange calendars (.ics) cannot be updated in calendar applications. This is due to a known issue following the Exchange security update from August 2026.
You can still access published calendars via a web browser.
Microsoft has confirmed the issue. A fix is scheduled for one of the upcoming updates.
The following clients are affected:
| Client | Result |
|---|---|
| Microsoft Outlook, Web Calendar Subscription | HTTP 500 |
| Apple Calendar on iOS and macOS | HTTP 500 |
| Google Calendar, Add a Calendar from a URL | HTTP 500 |
| Mozilla Thunderbird | HTTP 500 |
| Every script or automated consumer of the feed | HTTP 500 |
| Chrome, Edge, Firefox, Safari, Android Chrome, iOS, Safari | HTTP 200, Calendar returned |