insight rest api for executing an import

[Jon Hill]

https://insight-javadoc.riada.io/insight-javadoc-8.6/insight-rest/#import says that to run an Insight import via the REST API, I should be able to just POST to /start/import/<id>.

According to the insight-import log, the import I want to execute has an ID of 30, so for my test (on-prem), I posted to https://<server>/rest/insight/1.0/import/start/30 with no body, but all I got back was "Something went wrong.  Please contact the administrator."

Is this feature not available in Insight 6.4?