Endpoint User Name not populated when the username is equal to the mac-address of the device
Username field is not populated for a device.
VoIP phone username is not populated in Nac
If the username of a device is the mac-address, regardless if it is mac-authentication of 802.1x, it will NOT populate the username field. Some VoIP or IoT devices may use the mac-address as a username. If the mac-address is not different than the username we will not populate the username field.