To check to see if you need to recreate the standby NameNode, on the Ambari Server host:

curl -u <AMBARI_USER>:<AMBARI_PW> -H "X-Requested-By: ambari" -i -X GET <AMBARI_PROTO>://localhost:<AMBARI_PORT>/api/v1/clusters/<CLUSTER_NAME>/host_components?HostRoles/component_name=SECONDARY_NAMENODE

If this returns an empty items array, you must recreate your standby NameNode. Otherwise you can go on to Re-enable Standby NameNode.

Recreate your standby NameNode. On the Ambari Server host: curl -u <AMBARI_USER>:<AMBARI_PW> -H "X-Requested-By: ambari" -i -X POST -d '{"host_components" : [{"HostRoles":{"component_name":"SECONDARY_NAMENODE"}] }' <AMBARI_PROTO>://localhost:<AMBARI_PORT>/api/v1/clusters/<CLUSTER_NAME>/hosts?Hosts/host_name=<SECONDARY_NAMENODE_HOSTNAME>

Verify that the standby NameNode now exists. On the Ambari Server host:

curl -u <AMBARI_USER>:<AMBARI_PW> -H "X-Requested-By: ambari" -i -X GET <AMBARI_PROTO>://localhost:<AMBARI_PORT>/api/v1/clusters/<CLUSTER_NAME>/host_components?HostRoles/component_name=SECONDARY_NAMENODE

This should return a non-empty items array containing the standby NameNode.