Hi @Rob M ,
Based on my research, there may not be accurate query to produce a list of devices that are failing to register.
We could use device status to check it roughly.
For clients registered for the first time, we could filter the data for client label column is No, which could produce a list of devices that are failing to register roughly.
For clients that are not registered for the first time, we could filter the data for client activity label column is inactive.
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