When a multiple-node UMP is deployed in an environment where the secondary UMP node robot reports to a hub other than the primary (UIM Server) hub, alarms will not be displayed in UMP on the secondary node. This includes list views, dashboards, and USM.
There is an issue with the wasp probe where it assumes that the Trellis probe will be located on the hub that its robot reports to. Since Trellis only exists on the primary hub, and multiple instances of Trellis cannot be deployed in a single environment, the alarm API calls will fail.
Four hotfixes must be deployed to both UMP nodes:
ump_dashboard_8.4.2_HF1.zip
ump_listdesigner_8.4.2_HF1.zip
ump_listviewer_8.4.2_HF1.zip
ump_usm_8.4.2_HF3.zip
All of these are available on the UIM Hotfix Index page.
This is expected to be resolved in UMP 8.5.