Release : 9.1.0
Component : UIM - ROBOT
Most of the views in USM do not use the cm_nimbus_robot table but rather the cm_computer_system table.
Check to make sure you have probe_discovery queue from all of your hubs with a path back to the Primary hub.
Also increase the discovery_server loglevel to 5 and check the logs for communication errors from the discovery_server to the problem robots and resolve that issue if it exists.
Perform a discovery reset for the individual robots and allow them to re-populate.
The appropriate entry in cm_computer_system was created on 2020-08-05 09:28:40.393 ie. 5th of august which was not present when the case was opened. The only changes done in between is that the Primary hub was rebooted due to patching but the issue was resolved as a result. Tables examined: cm_nimbus_robot, cm_device and cm_computer_system.