Chirpstack v4 Downlink HTTP URL and JSON Format

Hi I’m using HTTP integration with my application, and I am getting the uplink data from the LNS.

However, I’m not able to send downlinks to my devices. I’m initially testing using postman. Below are the details:

URL : http://LNS_IP_HERE:8080/api/devices/DevEUI_HERE/queue
Headers: ‘Authorization’ : ‘API_KEY_HERE

    "deviceQueueItem": {
        "dev_eui": "*DevEUI_HERE*",
        "confirmed": false,
        "data": "AQID",
        "fPort": 11

I’m getting 400 Bad Request error for the above.

Note : I have installed the LNS locally but application is running on cloud.