What causes a DATA_DOWN_GATEWAY error?

I’ve had Chirpstack V3 running for ages with no issues. I added a second gateway on April 1st, no issues at all. I happened to take a look at some of the applications I have running and as of April 13th, I’m now seeing DATA_DOWN_ERROR errors showing up in the Errors graph. Since adding the gateway I haven’t made any other changes. Googling for this error didn’t yield any useful results.

What are these, and why would I suddenly start seeing them?

Under the device events tab, you will probably log items with more details. In general causes can be:

Maybe I don’t know what I’m looking for, but I don’t think v3 has a device events tab?

Also, the DATA_DOWN_ERROR doesn’t appear in the list of errors there? Unless that’s a high level error type, and the sub-error type would be one of those.

Please see Event logging - ChirpStack open-source LoRaWAN<sup>®</sup> Network Server.

As an alternative, you can also temporarily turn on JSON encoding (in the ChirpStack Gateway Bridge config) and inspect the gateway ack events.