Hello Lars Wegner,
This could be because of any of the following reasons,
- GPO not successfully applied on the clients/servers: Check a couple of devices to confirm if GPO is applied.
- Policy propagation: Sometimes, GPO changes might take time to propagate fully. This could be a reason if GPO is not applied to the devices.
- Reporting Delays: Confirm if the devices are able to communicate the status back to defender.
If all the above are checked, please reach out to support to address this further - Contact Us - Microsoft Support
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