Production cluster not visible from Kibana on monitoring cluster

I have a production cluster with 3 nodes all running 5.6.7. I also have a monitoring cluster with a single node also running 5.6.7.

I have configured everything as per this guide: https://www.elastic.co/guide/en/x-pack/5.6/monitoring-cluster.html. I have configured my production cluster to export the monitoring data to the monitoring cluster. I have verified that the data is being sent to the monitoring cluster and stored at the ".monitoring-es6-YYYY-mm-dd" indices. But in Kibana on the monitoring cluster data I can only see the local data (for the monitoring cluster itself).

All elasticsearch instances have a platinum license. I have restarted Kibana and both Elasticsearch clusters and the issue is still there.

Am I missing something else to view the monitoring data for the production clusters?