Cannot create Obs with REST, Invalid submission error

Development
1

I’m trying to create a new observation with REST services but I keep getting errors. When I post the data below

{
    "concept": "67a71486-1a54-468f-ac3e-7091a9a79584",
    "person": "24d85b48-ef69-4de0-91a4-e751bda85332",
    "obsDatetime": "2017-05-17T11:00:03.783",
    "encounter": "94d1e029-fc45-4601-b937-12a9c092c71a"
}

I get the error below,

{
  "error": {
    "message": "Invalid Submission",
    "code": "webservices.rest.error.invalid.submission",
    "globalErrors": [
      {
        "code": "error.noValue",
        "message": "error.noValue"
      }
    ],
    "fieldErrors": {
      "concept": [
        {
          "code": "error.null",
          "message": "Cannot be empty or null"
        }
      ]
    }
  }
}

When I post the following data,

{
	"concept": "67a71486-1a54-468f-ac3e-7091a9a79584",
	"person": "24d85b48-ef69-4de0-91a4-e751bda85332",
	"obsDatetime": "2017-05-17T11:00:03.783",
	"encounter": "94d1e029-fc45-4601-b937-12a9c092c71a",
	"value": "Something text here or concept uuid"
}

I get the following error.

{
  "error": {
    "message": "[value on class org.openmrs.Obs]",
    "code": "org.openmrs.module.webservices.rest.web.resource.impl.BaseDelegatingResource:748",
    "detail": "org.openmrs.module.webservices.rest.web.response.ConversionException: value on class org.openmrs.Obs\n\tat 
  }
}

It’s the same code I use when updating an observation, only that I change the url that I make the request to. I don’t seem to find the problem. Please advise.

2

In the first scenario, the error message indicates the concept is probably none existent. If the concept exists, what’s the datatype of the concept?