Cannot set User-type attribute using REST API

[Rei Song]

I am following the formatting of the JSON as shown on this guide, but I keep getting the following error:

{"errorMessages":[],"errors":{"rlabs-insight-attribute-55":"<Account Id> is not valid Object id or key"}}

Here is the payload I'm submitting for https://api.atlassian.com/jsm/insight/workspace/<workplace ID>/v1/object/create endpoint:

{
  "objectTypeId": "2",
  "attributes": [
    {
      "objectTypeAttributeId": "14",
      "objectAttributeValues": [
        {
          "value": "Blahblahblah"
        }
      ]
    },
    {
      "objectTypeAttributeId": "55",
      "objectAttributeValues": [
        {
          "value": "<Account Id>"
        }
      ]
    }
  ]
}

55 is the ID of the User-type attribute. I'm passing in the Atlassian ID (not the username/email address) as shown in the doc.

[Rei Song]

Never mind.. I realized I set the attribute type to an another Insight object (User list). I had to punch in the asset key instead of account ID and it worked.