Your organization uses Microsoft Defender for Endpoint (Microsoft Defender XDR). You need to ensure that all Windows 10 devices report their security health to Microsoft Defender for Endpoint. Some devices are showing as inactive. What is the most likely cause?
A missing or misconfigured Microsoft Defender for Endpoint sensor directly prevents telemetry from reaching the service, which is why devices appear inactive. Onboarding requires the sensor to be installed and running, with correct configuration, so any gap in that chain halts health reporting regardless of network or licensing state.
Why this answer
The Microsoft Defender for Endpoint sensor is the core component that collects and reports security telemetry from Windows 10 devices to the Defender for Endpoint cloud service. If the sensor is not installed, is missing, or is misconfigured (e.g., due to a corrupted installation or incorrect onboarding script), the device will appear as inactive in the Microsoft 365 Defender portal, even if the device is otherwise healthy and connected.
Exam trap
The trap here is that candidates often confuse device enrollment (Intune) with sensor onboarding, assuming that a device must be managed by Intune to report to Defender for Endpoint, when in fact any Windows 10 device can be onboarded via a simple script or GPO.
How to eliminate wrong answers
Option A is wrong because enrollment in Microsoft Intune is not a prerequisite for Defender for Endpoint reporting; devices can be onboarded via Group Policy, local script, or other methods without Intune. Option C is wrong because conditional access compliance policies control access to cloud apps, not the reporting of security health to Defender for Endpoint; a non-compliant device can still report telemetry. Option D is wrong because while internet connectivity is required for the sensor to communicate with the cloud, the question states some devices are inactive, not all; if connectivity were the issue, all devices would likely be affected, and the sensor would still attempt to report (showing as 'misconfigured' rather than 'inactive').