Unknown controller ‘user’.

I get an error:
Unknown controller ‘user’.

When calling the register:

https://sp-admin-cms.local/api/user/register/?username=unit%2Btest%40jpmedia.com.au&email=unit%2Btest%40jpmedia.com.au&user_pass=XXXX&nonce=XXXX&insecure=cool

I set a break point in json-api-user.php and see pimJsonApiController is called.
I set a break point in setUserControllerPath, but it does not seem to get called. I suspect this is the problem.