Issues synchronizing Outlook.com Calendars

The new version of our Outlook.com calendar authorization process does appear to be allowing users who were still affected by the incident to synchronize again.

Roughly half of the cohort we expect to be asked to relink have now been asked.

We are continuing to monitor but now expect any person experiencing issues who relinks their Outlook.com account to have their synchronization issues resolved.

We expect to close this issue tomorrow after all relink requests have been sent and we have monitored the situation for a while longer.

Please contact support@cronofy.com if you have any further questions.

We have released a new version of our Outlook.com calendar authorization process that we believe will allow users still affected by the incident to synchronize again. Unfortunately this will require users to reauthorize Cronofy's access to their Outlook.com calendar, as we have been unable to find a solution that would avoid this for the remaining calendars.

The Outlook.com accounts still encountering errors will receive relink emails over the coming hours requesting they reauthorize Cronofy's access to their calendar. This should then resolve their calendar synchronization problems. Only those whose synchronization was not fixed by yesterday's change will be required to relink.

We are continuing to monitor the affected users as this process takes place.

Please contact support@cronofy.com if you have any further questions at this time.

We’re still working on this incident as a priority. From our observations, we see that from 15:00 UTC yesterday, service would have resumed for most Outlook.com users.

We are working on restoring services for the remainder of the affected users.

Please do get in touch with us at support@cronofy.com with any questions.

It appears that Microsoft have made a change to the Outlook.com API we are using.

To be clear both Microsoft 365 domains and on-premise Exchange calendars are unaffected by this issue.

The earlier fix for Outlook.com involved adding a previously optional header to our requests, and resolved the issue for a little over 90% of Outlook.com accounts (not everyone as early signs indicated).

Further attempts to work around issue have so far been unsuccessful. We are attempting to get assistance from Microsoft on the underlying issue.

Please contact support@cronofy.com if you have any further questions or have customers that are still affected.

We now believe this incident to be resolved. We will continue monitoring to ensure there are no outstanding issues.

Please contact support@cronofy.com if you have any further questions at this time.

Upon further investigation, we have identified that a change made by Microsoft has impacted our ability to sync Outlook.com profiles.

We are exploring possible workarounds to this issue, whilst liaising with Microsoft Support for further assistance.

If you have any further questions at this time please reach out to support@cronofy.com.

We have identified an issue affecting some Outlook.com calendars. Customers may observe this issue as delays or failures when synchronizing with Outlook.com calendars.

We are investigating and will update you as we progress.