Possible ZHA bug with Zen Thermostat

Configuration Zigbee
1

From September 2023 until May of 2025, I used the Zen Zigbee Thermostat without issue. I use ZHA with a Sonoff dongle plus.

In May 2025, I started to have responsiveness issues with the thermostat - commands sent from Home Assistant wouldn’t register on the thermostat, giving this error: “Failed to perform the action climate/set_temperature. Failed to send request: Failed to send request: <Status.NWK_NO_ROUTE: 205>”.

Commands sent from the thermostat, however, would be reflected in Home Assistant immediately. I spent a small amount of time troubleshooting, and then essentially moved to a Venstar T2000 mini. I’ve since had some time to run down the issue with the Zen thermostat, and I’ve become convinced that it’s a bug in ZHA or Home Assistant. Obviously the error indicates that it’s a network/transport issue, but I’m convinced that’s because of software, not hardware or network setup.

Troubleshooting steps I have taken:

  1. Upgraded the Sonoff firmware with the HA add-on.
  2. Changed zigbee channels. No difference on 20 or 25.
  3. Changed 2.4.ghz wifi channels. No difference on 6 or 11.
  4. Removed the ZHA integration and all associated data and rebuilt it from scratch.
  5. Reinstalled HA and rebuilt my entire system from scratch.
  6. Moved the thermostat directly next to the Sonoff dongle. LQI is now 255, but the problem persists.
  7. Switched to Zigbee2MQTT - the thermostat works perfectly under Z2M, but unfortunately the thermostat card that is paired with the thermostat under Z2M is terrible, and I haven’t found a way to fix/customize it yet.

So here’s where I am now: The thermostat is set up in a test-bench scenario directly next to the zigbee dongle. If I remove it and then reconnect it, it will work perfectly for anywhere from 5 minutes to an hour, and then sent commands stop working. Commands sent from the thermostat to HA are reflected immediately, and the indicator on the thermostat shows that it’s connected to the zigbee network.

My three theories as to the root cause are:

  1. HA update changed something
  2. ZHA update changed something
  3. HA pushed a firmware update to the thermostat which caused an incompatibility. I’m currently showing firmware 0x0000021f, which is not the firmware version format I’ve seen other places.

My guess is that it’s #2, but I’m not sure.

Does anyone have any ideas about what might be happening? Any other Zen thermostat users with this problem? I don’t like the Venstar (the temperature sensor is very jumpy and inaccurate), so I’d like to get back to using the Zen at some point.

If needed, I do have some debug logs that ran while having this communication issue. Also, I did ask this question in the Discord with no responses.

Thanks!

2

I may have missed it, but I can’t see any details about your thermostat in your post - model number etc.- so it’s difficult to check.

If you look at the issues page for ZHA device handlers there are a number of reports which may be useful:

If it works with Z2M but not with ZHA that suggests there is something unusual about the implementation of Zigbee in the thermostat. ZHA is designed to work with any compliant device, Z2M creates custom handlers for every device.

3

This is the Zen Thermostat, identified in ZHA as the “Zen-01 by Zen Within.”

Thanks for the link - I was wondering if I should take this issue directly to the ZHA github. I’ll dig there and see what’s up. I would believe there’s a nonstandard Zigbee implementation, but it did work absolutely flawlessly for about 18 months before this issue arose, so I’m still inclined to think something changed.

4

Is it the time of year, or is there a flood of similar issues popping up with unreliable connectivity to thermostats?

I’ll let you search the forums, but there seems to be a lot with similar problem descriptions.

Looking like a protocol reliability issue, rather than individual integrations being faulty.

Trends…

5

The exact thing happened with my Zen Thermostats. I have two. The same timing and everything. Something has definitely changed that cause them both to become extremely unreliable. Glad to partner on identifying the issue, but I’m not entirely sure where to start.

6

Hey, that’s great to have another data point. I’m also not really sure where to start, so maybe we can manage to attract the attention of someone with a lot more backend knowledge than either of us have.

7

Another data point here. Just bought a zen Thermostat and set up a new Zigbee server with an RPi5 and the SONOFF Zigbee Antenna. Tried setting it up for the first time and I get the same issue with the error logged above.

I am not your backend knowledge solution, though. Has anyone contacted HA about it?

8

Thanks so much for another data point - I think our best bet at this point is probably to file a bug report on the ZHA github - I do have a github account and can do that, but never have before, so I’m slightly intimidated by that.

9

!I have the same issue with a new device…is there any news ?
I use zha with SONOFF TRVZB via CC2652
ITead_Sonoff_Zigbee_3.0_USB P latest firmware

[546939150208] Error during service call to climate.set_temperature: Failed to send request: Failed to send request: <Status.NWK_NO_ROUTE: 205>

Input direction works and pairing did work without any problems