Hi,
In order to scan for missing updates the machine needs to be running. There is no way that machines are turned off and you can scan for updates.
Update 1:
You can find some sample queries of how to get available updates in the official documentation. Keep in mind that the data is available for the past 30 days. If the machine was not started for more than 30 days the data will not be available. Information how to run resource graph queries with PowerShell.
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