Grafana is installed and data collector successfully configured. Alarm queries function.

DCIs are visible in enumeration query, but actually trying to graph a DCI results in an error:
Grafana:

Object
xhrStatus:"complete"
request:Object
method:"GET"
url:"api/datasources/proxy/1/grafana/datacollection"
data:null
params:Object
interval:600000
from:_
to:_
targets:"[{"dci":{"name":"xxxxxxxxxx-removed","id":"190615","$$hashKey":"object:518"},"dciTarget":{"id":"20810","name":"xxxxx-removed"},"legend":"xxxxx-removed","refId":"A","type":"DCI"}]"
response:Object
description:"org.json.JSONArray.iterator()Ljava/util/Iterator;"
error:46

Tomcat:

org.netxms.websvc.WebSvcStatusService                   | Internal error
java.lang.NoSuchMethodError: org.json.JSONArray.iterator()Ljava/util/Iterator;