Device Queue Downlink problem

Hi!
I am testing downlink via api with DeviceQueueService : [POST] api/devices/{device_queue_item.dev_eui
My example is body:
{
“reference”: true,
“confirmed”: “true”,
“fPort”: 5,
“data”: “eyJkYXRhIjo”
}
and device_queue_item.dev_eui HEX from device but it throws an error:

Response Body

{
  "error": "f_port must be > 0",
  "code": 3,
  "message": "f_port must be > 0",
  "details": []
}

What I am doing wrong?
Thanks!

@TheHysiK

Use below example body
POST: http://localhost:8080/api/devices/{device.eui}/queue

{
      "deviceQueueItem": {
        "reference": true,
        "confirmed": true,
        "data": "AAA=",
        "fPort": 1
      }
    }

Thanks! When trying example I did not removed json so problem was using json and data…
Regards!