As far as I can tell, keyspace notifications are not sent to the slave, because the data manipulations themselves are sent to the slave, which can have its own keyspace notifications set.
To get keyspace notifications on the slave, you need to be running 2.8+ on the slave, and you need to set the keyspace notification configuration to what you need, then subscribe to those notifications on the slave.
If you are still having difficulties after you have properly set your configuration on the master and slave, please report what you are seeing from INFO on both the master and slave, as well as the output of "redis-cli config get notify-keyspace-events" for both the master and slave.
- Josiah