Downlink shows as scheduled, but is no longer sent to my device or gateway


I used the downlink feature successfully before, but lately it just does not send downlink packets to my device. This is my console log for the device i am trying to send data to:
As you can see, uplink packets come to TTN and a downlink packet is scheduled. But it is never sent. The gateway also does not show the packet…

What might be causing this?

I think the MQTT error topics don’t report too much, but maybe you’re lucky, so I’d surely subscribe to all events of the MQTT Data API to see if the downlinks are sent, and if you’re getting any error: +/devices/+/events/#

When clicking the uplinks in TTN Console you’ll see some more details:

  • Anything special when you click the uplinks on the application/device’s Data page?

  • When looking at the metadata of an uplink in the Data page: how many gateways received the uplinks? Any chance one of them is not a true gateway, but a single channel forwarder (which should not be used on TTN)?

  • Likewise: anything special when clicking uplinks on the gateway’s Traffic page?

  • TTN Console is not always 100% reliable: does the device indeed not receive any downlink?

  • Have you always been using confirmed downlinks? What if you replace the scheduled downlink with a new one? Maybe TTN is still awaiting a confirmation of an earlier one, and is still using another gateway (or single channel forwarder…) to repeat that downlink. (Though maybe that would also show in the application/device’s Data page. Also, I am not sure how “replace” would work in that case.)

  • What gateway are you using? Anything in its logs?

Thank you @arjanvanb looking at the MQTT gave me the information, that my encoder was having an error with the data that should be sent to the device. It now works without issue.

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