Connections on cluster not being logged

I have postgresql 9.4 on a cluster, hardware based. I need to be able to
see which users are connecting to which database and when to be in
compliance with our security policies.

I have set the following in the postgresql.conf and did a pg_ctl reload:

log_connections = on
log_line_prefix = '%t [%p]:[%u]:[%h]-[%d] [%1-1]'

Unfortunately, it doesn't seem to be logging the connections. This is what
I have used on our non-clustered instances and it's working as expected.
Have I missed something relating to logging on a cluster? The second node
is strictly for automatice failover, so nothing is actually running there
at the moment.

Thank you in advance for any suggestions.

Sandy