Hello @Nikita Ustiuzhanin thank you for reaching out. Missing change notifications can happen due to a number of reasons:
- User's password has been reset
- User's device is out of compliance
- User's account has been revoked
When such an event happens, Microsoft Graph sends a special lifecycle notification,
subscriptionRemoved. Microsoft Graph also sends another lifecycle notification,
missed, if a change notification cannot be delivered to an app. Please see documentation on webhooks-lifecycle to see how to handle these notifications to ensure continuity.
Please let me know whether this helps and if you have further questions,