Trouble sending data to TTN Device Downlink via MQTT Out

General
1

I a looking to troubleshoot sending commands to my downlink of my device on the TTN network.

In the TTN console I do this and it works:
image

But from Node Red I have the following in a function feeding into a MQTT Out and it does not work: [Device and App ID are of course REPLACED as to not share them]

// TTN downliank settings
var dev_id = "REPLACED"; // from previous MQTT received message in this case;
var dlPort = 2; // downlink port in this application
var dlConfirmed = true;
var dlScheduled = "replace"; // allowed values: "replace" (default), "first", "last"

// MQTT settings
msg.topic = "v3/REPLACED@ttn/devices/" + dev_id + "/down/push";
msg.qos = 0;
msg.retain = false;

var payload_raw = Buffer.alloc(2, 0);
payload_raw[1] = 0x12c; // Changed uplink fequency to 5min (300 sec in Hex)
var base64data = payload_raw.toString('base64');

// use payload fields
var message = {
    port: dlPort,
    confirmed: dlConfirmed,
    schedule: dlScheduled,
    payload_raw: base64data,
};

msg.payload = message;

return msg;

I was referencing this post:

and this post:

as starting points but have hit a dead end for now. Any help is appeciated.

2

I wondered if my example was too old so I looked up The Things Stack current documentation and found it here:
https://www.thethingsindustries.com/docs/integrations/mqtt/#publishing-downlink-traffic

So I updated my function node to this:

msg.topic = "v3/REPLACED@ttn/devices/REPLACED/down/push";
var base64data = msg.payload;

msg.payload = {
    "f_port": 2,
    "frm_payload": base64data,
    "priority": "NORMAL"
};

return msg;

And I am passing the base64 encoded values for the seconds in as the msg.payload.

Possible values I am passing:
Hex			Time			Base64
0100012C = 300 secs (5 mins)	xKw=
01000258 = 600 secs (10 mins)	yZg=
01000384 = 900 sec (15 mins)	zoQ=
010004B0 = 1200 sec (20 mins)	0rA=
01000708 = 1800 sec (30 mins)	3Ig=
01000E10 = 3600 sec (1hr)		4LiQ

Here is part of the debug output to show a payload example.
image

But even still I have yet to seem to get this to work.

And thoughts on how to even troubleshoot this would be good as I do not even know if the command from Node Red is reaching the TTN application. None of the live data views show it.