After an upgrade, the NS does not show up as a monitored resource.
8.7.1
Include the Notification Server machine 'resource target' in any agent-based monitor policy (or create a separate agent-based monitor policy with at least 1 metric rule) and receive it via the SMA refresh policy on the Notification Server.
Now, the Notification Server is shown as a "Monitored resource" and RTPV shows all available agentless or agent-based metrics