Onboarding Devices: "No authenticated user found"

Hi, 

I am looking to onboard a device in Purview for the purpose of testing some Endpoint DLP policies. 

I have ran the onboarding script locally and the device successfully appears on the 'Devices' screen.

'Real time protection/RTP' and 'Behavior monitoring/BM' both show as 'enabled' with a green tick, however under 'Valid User' it has a red cross and states: "Invalid: No authenticated user found. Without proper authentication, data classification is impeded. To ensure precise validation, we recommend re-onboarding to Active Directory".

The device is in active directory. I have signed into the device with an account that is also in Active Directory.

Is there anything additional that I need to do?

Any help would be really appreciated - thank you!!!