Microsoft 365 Alert – Service Degradation – Microsoft Defender XDR – Some admins may see alerts for sensor connectivity issues in Microsoft Defender for Identity – RESOLVED

Announcements Arpan Das

19/05/2026 09:15:00 AM

NHSmail Reference: INC46830338

Microsoft Reference: DZ1315691

Issue Status: RESOLVED

Issue Description: Users may see alerts for sensor connectivity issues in Microsoft Defender for Identity.

More info: This issue specifically affects some Microsoft Defender for Identity V3 sensors, with alerts surfaced in the Microsoft Defender portal.

Admins may see health alerts indicating disconnected sensors, and newly deployed V3 sensors may fail to start.

Sensors continue to send data, so there’s no data loss. However, because sensors are disconnected from configuration, delays may occur in AD sync operations.

Final Update: 20/05/2026 09:25:00 AM–Microsoft has confirmed that the fix, now fully deployed, successfully resolved the issue.

Scope of impact: Your organization is affected by this event, and some admins relying on Microsoft Defender for Identity V3 sensor data may be impacted. This information may be updated as their investigation continues.

Root cause: A certificate change is causing authentication issues within a core section of the Microsoft Defender for Identity service, leading to sensor disconnections.

Next Steps: Microsoft are reviewing the configuration of the affected authentication component to identify how the misconfiguration occurred and prevent recurrence.