Error callbacks are a subtype of custom callback.
There can be only two kind of error callbacks.
Callback severity field value will be: WARN.
Callback info field value will be: Sigfox network experiencing issues that could cause message loss or delay for some devices.
This means that one of the stations that caught one of the previous 5 messages coming from this device is currently not communicating (COM_STATUS down).
Callback severity field value will be: ERROR.
Callback info field value will be: No message received since <Date and time of last received message>
This means that the keep-alive has been breached, it is sent when the keep-alive is breached and will not occur before it is breached again (meaning before a message has been received and then a new breach occurred).