According to the Sentinel Servers page in NSMAdmin, I have 6 sentinel
servers all running v2.00.03. The next column reports "status 0"

On the servers themselves, the Sentinel and Event monitor screen reports
"Event: NO" which I would expect and "Sentinel: NO" which I would have
thought should says YES.

Despite all the sentinels, the work is all being done on the engine server.

What have I done wrong?

Some sentinels are on the same subnet as the engine server, others are
behind a firewall which only allows NCP. Some of the servers are cluster
nodes, but none of them report "Sentinel: Yes"

Any help appreciated