Hello,
I have sensors via zigbee2mqtt and for some sensors after a certain time I get the following message displayed « No temperature recorded recently. »
This is not a battery problem but a receiver issue (currently CC2531 but CC2652RB on its way 
).
My question is: Can we currently retrieve the state of no data reception from a device to trigger a scene?
Hello, do you have access to the z2mqtt logs?
I have the same issue as you, but it might be due to a different cause: if I slightly move my receiver, which can disconnect it for 0.001 seconds from the Raspberry Pi, then Zigbee2mqtt crashes and no longer allows Gladys to retrieve the data sent by the sensors.
I added a USB extension cable as recommended in the zigbee2mqtt documentation (interference), now I no longer have disconnections, but the connection LQI is not great, averaging 15 for the problematic sensors.
Regarding the key change, since my network will eventually exceed 20 devices, the CC2531 is no longer suitable.
This is not currently possible, but there is a feature request in this direction:
Ability to receive an alert when a sensor no longer reports a value!