Reply To: Tutorial says broker = 192.168.x.x – what address do I put in for Hermetry?

Yes. That blog is for a broker on your own home network, that’s why it has a 192.168 address. For Hermetry there’s no IP you should use at all: connect by the host name from the Connection details card, TLS on 8883. TLS needs the name (SNI), so the pinged IP fails, and plain 1883 is refused unless the profile allows plain MQTT, which it doesn’t by default. rc=5 is “not authorised”, and the actual reason ends up on the device’s Log tab, worth a look.

import ssl, json, paho.mqtt.client as mqtt

HOST = "<host from Connection details>"
TOKEN = "<access token>"

c = mqtt.Client(client_id="reefer-01")
c.username_pw_set(TOKEN)                  # token as username, no password
c.tls_set(cert_reqs=ssl.CERT_REQUIRED)    # normal public CA bundle
c.connect(HOST, 8883, keepalive=60)
c.loop_start()
c.publish("v1/telemetry", json.dumps({"temperature": -18.2}), qos=1)

With paho 2.x you need mqtt.Client(mqtt.CallbackAPIVersion.VERSION2, client_id="reefer-01") instead.