mad-hatter query node returns 500

The query interface is only available on Couchbase nodes running the query service.

Received error 500 when contacting the query service on this node. You can try refreshing the browser, or connecting to another node (if available).

The query service should be found on the following nodes:

http://172.23.120.203:8091/ui/index.html#!/query/workbench

http://172.23.121.43:8091/ui/index.html#!/query/workbench

http://172.23.122.202:8091/ui/index.html#!/query/workbench

 Note that the above links are provided as a convenience. They may not work if you are accessing the Web Console via a web proxy or if Couchbase Server has been deployed in a split horizon DNS environment, with public and private hostnames and IPs. In the event the links don't work, log directly into the node.