Why are some computers missing from my HealthCheck for Office 365 overview?
You must install the Device Management Agent (DMA) on customer computers in order for the HealthCheck for Office 365 assessment to run. If some users' scans don't show up in the HealthCheck for Office 365 overview, it's possible that DMA is not installed on their computers.
DMA can be installed on customer computers by sending an email request, or through a Group Policy Object (recommended). Read the following Knowledge Base articles to learn more: