Link Xray test Execution with Test plan when importing - selenium

[Ryan Tee Kwee Teck]

I am using Rest API - to import selenium result back to the Xray

rest/raven/1.0/import/execution/cucumber/multipart

When I import without enter the custom field ( test plan ) - it's working fine.

{
  "fields": {
    "project": {
      "id": "20600"
    },
    "labels": [
      "Automation"
    ],
    "summary": "Test Execution - Automation",
    "issuetype": {
      "id": "10007"
    }
  }
}

 When I import with the test plan field -it's return me 400 error code.

I get customfield id is using ?expand=names, so i think the ID should be correct, and the value I put inside ( NAS-6871 is the test-plan ID which already exist in Xray.

Any more setup i need to do to enabled this linkage to be work?

{
  "fields": {
    "project": {
      "id": "20600"
    },
    "labels": [
      "Automation"
    ],
    "summary": "Test Execution - Automation",
    "issuetype": {
      "id": "10007"
    },
    "customfield_24724": [
      "UNI-6871"
    ]
  }
}

Also, I Couldn't see edit Icon in the Test Plan field there compare to labels, is there any more setup i need to do?