PostgreSQL 9.6 log shipping replication stuck on startup
Thanks to Luan Huynh, I checked the logs on the Slave and saw that it was not able to start WAL streaming due to the missing replication slot on the Master (I really was certain it had been created! :-) )

Creating the replication slot with pg_create_physical_replication_slot was all that was needed.  Verifying the replication slot with SELECT * FROM pg_replication_slots showed the slot had been created and WAL streaming was active.

I was able to verify that the latest records on highly active tables on the Master are being successfully replicated on the Slave.