Using user API to get built-in users

Elastic Security
1

Hello, I am hoping to get some help please.

I have a version 7.17 Elasticsearch and using the dev tools, I run

GET /_security/user
but I get

{
  "error" : "Incorrect HTTP method for uri [/_security/user?pretty=true] and method [GET], allowed: [POST]",
  "status" : 405
}

but this works on another instance the same version

So I try using POST with

POST /_security/user

but I get

{
  "error" : {
    "root_cause" : [
      {
        "type" : "parse_exception",
        "reason" : "request body is required"
      }
    ],
    "type" : "parse_exception",
    "reason" : "request body is required"
  },
  "status" : 400
}

I am not even sure how to proceed from here, please assist, thanks