I can’t seem to figure out how to get a sigfox downlink working. I tried following the guide in the docs, but the sigfox callback returns with an error 502: bad gateway.

Under the callback configuration on the sigfox backend I left the verification-code header empty as it says optional and “Use the same text input during the device creation at TagoIO.” isn’t very helpful in explaining where to find this code. Hope this missing header isn’t the issue, but I don’t believe so.

Also when checking the messages of my test device on the sigfox backend the downlink callback message is given as:
Downlink status - ErrorClose

• Status : [INVALID_PAYLOAD]
• Data (Hexa) : N/A

This makes me believe my configuration parameters are wrong, but I can’'t find any information on how the Device Configuration Parameters work. Can someone point me in the right direction? Sigfox expects up to 8 bytes of data but I have no idea how to write my desired payload in the device configuration, as a string in hex as a number?