Thrown by NatsBroker.connect when the NATS server rejects the
JetStream manager probe — the server does not have JetStream enabled, which
the nats broker requires. The platform's own error (typically the raw
503 / NO_RESPONDERS reply for the $JS.API subjects) is carried as
cause.
Remedies: start the server with the -js flag, or enable jetstream in
its configuration file.