HID Approve OOB Registration

Question

So , am using HID Approve to register a user using Out Of Band using the code below in Vscode:

POST {{base-url}}/scim/FTRESS/v2/Authenticator/34825840
Authorization: Bearer {{token}}
Content-Type: application/scim+json

{
    "schemas": ["urn:hid:scim:api:idp:2.0:Authenticator"],
    "urn:hid:scim:api:idp:2.0:Action": {
        "action": "AT_CUSTOOB"
    },
    "activationCode": "Pass0001",
    "owner": {
        "display": "EUSER",
        "value": "34825840"
    },
    "policy": {
        "value": "AT_CUSTSMS"
    }
}

The error am getting is belowly stated:

{
  "schemas": [
    "urn:ietf:params:scim:api:messages:2.0:Error"
  ],
  "detail": "action AT_CUSTOOB does not exists",
  "status": "400",
  "scimType": "invalidValue",
  "errorCode": 0
}

What might be the error because it cannot be traced from the HID Documentation provided plus all the resources in the internet

POST {{base-url}}/scim/FTRESS/v2/Authenticator/34825840
Authorization: Bearer {{token}}
Content-Type: application/scim+json

{
    "schemas": ["urn:hid:scim:api:idp:2.0:Authenticator"],
    "urn:hid:scim:api:idp:2.0:Action": {
        "action": "AT_CUSTOOB"
    },
    "activationCode": "Pass0001",
    "owner": {
        "display": "EUSER",
        "value": "34825840"
    },
    "policy": {
        "value": "AT_CUSTSMS"
    }
}

result was:

{
  "schemas": [
    "urn:ietf:params:scim:api:messages:2.0:Error"
  ],
  "detail": "action AT_CUSTOOB does not exists",
  "status": "400",
  "scimType": "invalidValue",
  "errorCode": 0
}