Hi,
Thank you for your question. I reproduce this on my environment using:
GET https://graph.microsoft.com/v1.0/deviceAppManagement/mobileApps/{ID}/deviceStatuses
But I also encountered the same error which is Bad Request - 400 "Resource not found for the segment 'deviceStatuses'.
I checked the documentation and cannot locate it also. It may have been removed since it is under beta.
Important: Microsoft Graph APIs under the /beta version are subject to change; production use is not supported.
I suggest providing feedback on the documentation itself to put alternatives for deviceStatuses or to further verify if they have removed it.
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