When you select discovery_agent resides on secondary hub, and try to launch discovery wizard,
it does not work with error "Unable to acquire version information"
The error indicates communication failure in between discovery_agent probe and ump robot.
if secondary hub (where discovery_agent probe resides on) is connected to primary hub without tunnel,
verify 48*** range port access from ump robot to secondary hub including discovery_agent probe port.
if secondary hub (where discovery_agent probe resides on) is tunnel client, connected to primary hub tunnel server,
verify 48*** range port access from ump robot to the primary hub including tunnel-proxy-port in the primary hub.
tunnel-proxy-port in the primary hub is very crucial port in this senario which acts as proxy point for all the requests to tunnel client secondary hub.
the tunnel-proxy-port is visible in tunnel server side hub GUI - [Hubs] tab - [Source] column for secondary hub entry.