Downlink packet using Rest API: how to set jsonObject correctly

@fmgst @brocaar I was able to figure out my issue. I am able to transmit with the following with removing the jsonObject and choosing no CODEC

{
  "deviceQueueItem": {
    "confirmed": true,
    "data": "eyJ0ZW1wZXJhdHVyZSI6IDIyLjV9",
 "devEUI": "536f6c6172613031",
    "fCnt": "0",
    "fPort": "1"
  }
}

The issue was that my device that I was using was not connected at the time and I was receiving the following error response

{
  "error": "enqueue downlink payload error: get next downlink fcnt for deveui error: rpc error: code = NotFound desc = object does not exist",
  "code": 13,
  "message": "enqueue downlink payload error: get next downlink fcnt for deveui error: rpc error: code = NotFound desc = object does not exist",
  "details": []
}

I was interpreting this as the jsonObject was not defined which was not correct. This led me to believe that I needed to use a CODEC and over complicate my issue. The error actually meant that I could not assign the fcnt to the deveui (I know if explicitly says in the error code). From there I determined that I need the device activated (joined) to the network. After joining I tried sending the above without a jsonObject and got the same issue as this post.

After sending an uplink with my node I was able to queue a downlink and get the 200 response code.

I did this 4 times and then checked the response from the get command and got the following response:

 {
  "deviceQueueItems": [
    {
      "devEUI": "536f6c6172613031",
      "confirmed": true,
      "fCnt": 0,
      "fPort": 1,
      "data": "eyJ0ZW1wZXJhdHVyZSI6IDIyLjV9",
      "jsonObject": ""
    },
    {
      "devEUI": "536f6c6172613031",
      "confirmed": true,
      "fCnt": 1,
      "fPort": 1,
      "data": "eyJ0ZW1wZXJhdHVyZSI6IDIyLjV9",
      "jsonObject": ""
    },
    {
      "devEUI": "536f6c6172613031",
      "confirmed": true,
      "fCnt": 2,
      "fPort": 1,
      "data": "eyJ0ZW1wZXJhdHVyZSI6IDIyLjV9",
      "jsonObject": ""
    },
    {
      "devEUI": "536f6c6172613031",
      "confirmed": true,
      "fCnt": 3,
      "fPort": 1,
      "data": "eyJ0ZW1wZXJhdHVyZSI6IDIyLjV9",
      "jsonObject": ""
    }
  ],
  "totalCount": 4
}

@fmgst I appreciate your quick response and trying to help with this issue! I will look into that node design and see what I can use for my own implementation.