My zigbee2mqtt suddenly stopped working!

Configuration Zigbee
1

Help!
Suddenly, 2 hours ago my zigbee2mqtt stopped, and I’m totally unable to get it back to life!
I have an slzb-mr4u adapter, using the CC2674P10 part as a zigbee controller.
It had been working very well for two months when, suddenly without any changes being done to the system, lights and everything else died!
I even tried

  1. using the USB interface of the MR4U
  2. using an older Sonoff zigbee 3.0 P
  3. restoring version zigbee2mqtt version 2.7.2 from a backup

But nothing helped.
Maybe something strange has happened elsewhere in the system?
It’s HAOS 17.1, HA 2026.2.3.
Help, please!

My config:

data_path: /config/z2m
socat:
  enabled: false
  master: pty,raw,echo=0,link=/tmp/ttyZ2M,mode=777
  slave: tcp-listen:8485,keepalive,nodelay,reuseaddr,keepidle=1,keepintvl=1,keepcnt=5
  options: "-d -d"
  log: false
mqtt:
  server: mqtt://192.168.10.41:1883
  user: myuser
  password: mypassword
  base_topic: z2m
serial:
  port: tcp://slzb-mr4u.local:7638
  baudrate: 115200
  adapter: zstack


[21:54:25] INFO: Preparing to start...
[21:54:25] INFO: Socat not enabled
[21:54:26] INFO: Starting Zigbee2MQTT...
Starting Zigbee2MQTT without watchdog.
[2026-02-25 21:54:26] info: 	z2m: Logging to console, file (filename: log.log)
[2026-02-25 21:54:26] info: 	z2m: Starting Zigbee2MQTT version 2.8.0 (commit #unknown)
[2026-02-25 21:54:27] info: 	z2m: Starting zigbee-herdsman (9.0.2)
[2026-02-25 21:54:27] info: 	zh:zstack:znp: Opening TCP socket with slzb-mr4u.local:7638
[2026-02-25 21:54:27] info: 	zh:zstack:znp: Socket connected
[2026-02-25 21:54:27] info: 	zh:zstack:znp: Socket ready
[2026-02-25 21:54:27] info: 	zh:zstack:znp: Writing CC2530/CC2531 skip bootloader payload
[2026-02-25 21:54:28] info: 	zh:zstack:znp: Skip bootloader for CC2652/CC1352
[2026-02-25 21:54:46] error: 	z2m: Error while starting zigbee-herdsman
[2026-02-25 21:54:46] error: 	z2m: Failed to start zigbee-herdsman
[2026-02-25 21:54:46] error: 	z2m: Check https://www.zigbee2mqtt.io/guide/installation/20_zigbee2mqtt-fails-to-start_crashes-runtime.html for possible solutions
[2026-02-25 21:54:46] error: 	z2m: Exiting...
[2026-02-25 21:54:46] error: 	z2m: Error: Failed to connect to the adapter (Error: SRSP - SYS - ping after 6000ms)
    at ZStackAdapter.start (/app/node_modules/.pnpm/[email protected]/node_modules/zigbee-herdsman/src/adapter/z-stack/adapter/zStackAdapter.ts:107:27)
    at Controller.start (/app/node_modules/.pnpm/[email protected]/node_modules/zigbee-herdsman/src/controller/controller.ts:143:29)
    at Zigbee.start (/app/lib/zigbee.ts:70:27)
    at Controller.start (/app/lib/controller.ts:101:13)
    at start (/app/index.js:149:5)
2

I, too, am having unreliable MQTT. This is Govee, though.

3

After several attempts with connecting the adapter to usb, usb+poe, only poe, including saying please please, it started working again.
But today the same crash happened again! And I’m not at home to try all the different approaches from last time.
This is very frustrating! Please help, somebody!

4

I use to experience issues, too. I hardcoded the mqtt settings and updated the port for my coordinator to use /dev/serial/by-id/, as-is recommended by the devs and many on this forum. Been running smooth ever since.

mqtt:
  server: mqtt://core-mosquitto
  user: <user>
  password: <password>
  keepalive: 60
  reject_unauthorized: true
  version: 4
serial:
  port: >-
    /dev/serial/by-id/usb-Nabu_Casa_SkyConnect_v1.0_1676147856e2ed11ac5ef75162c613ac-if00-port0
  adapter: ember
  baudrate: 115200
  rtscts: false

EDIT To find the port by-id, go to Settings > System > Hardware > click “all hardware” scroll down and you should find something like ttyUSB0 with the full path of your coordinator (as long as your coordinator is plugged directly into your HA machine).

5

Followed that link in your error and they have this regarding your specific error -

Error: SRSP - SYS - ping after 6000ms for zStack or HOST_FATAL_ERROR for EmberZNet

Common reasons for this error:

  1. The port of your serial adapter changed. Check this to find out the port of your adapter.
  2. If you are using a CC2530 or CC2531; it is a common issue for this adapter to crash (due to its outdated hardware). Reflashing the firmware should fix the problem. If it happens often consider flashing the source routing firmware or upgrade to a more powerful adapter.
  3. Your adapter requires additional configuration parameters. Check supported Adapters section to find out if your adapter requires extra parameters (eg. ConBee II / RaspBee II).
  4. Home Assistant’s “Zigbee Home Automation” (ZHA) integration is enabled. Try to disable the ZHA integration and restart the Zigbee2MQTT add-on.
  5. Your hardware adapter is flashed with the router firmware and not with the coordinator firmware.
  6. Your network Zigbee adapter is not accessible over the LAN network.
  7. Another software on your machine (including Home Assistant integration) is interfering with USB devices (example: HA EDL21 integration trying to find a USB device)
6

Instead of using the local domain name for your coordinator try it’s IP-address:

port: tcp://coordinator-ip-address:7638

7

It’s connected and powered via PoE and tcp-connection.

8

Tried. Same problem.

9

I checked these. Since the MR4U is a new adapter, I tried replacing it with a USB adapter as you can see in my opening post. It failed with that as well. Same error.
So I think the problem is elsewhere. It’s strange that it worked for two weeks and then failed.

10

Then “port” can not be tcp. Find the correct USB port the coordinator is connected to.

Should look something like the below with Z2M’s configuration.yaml:

serial:
  port: >-
    /dev/serial/by-id/your-coordinator

Also don’t forget to change these settings within the coordinator’s settings through the SLZB UI.

11

Why do you say it has to be connected to USB? It worked very well over tcp and powered by PoE for two months before it started crashing. And after the first crash it suddenly started working again for two weeks. But I did try it on USB as well the first time. There was no change. I suspect that the problem is caused by something else, but I have no idea what that might be

12

Start with the basics. Can you reach the embedded web interface for your device?
If so, can you check that the details match what you have in your Z2M config?
Asking because I can see you’re using port 7638 in your Z2M config, but that port is usually 6638.

13

He didn’t say that. He said when you connect via USB, be it MR4U or Sonoff dongle, during your troubleshooting attempts, you will have to change the configuration to tell zigbee2mqtt to connect via USB… and obviously the path via USB to MR4U and to Sonoff dongle would be different.

So, similarly, when you connect via PoE, you will want to tell zigbee2mqtt the correct path (and port) to your zigbee router.

So the error message is zigbee2mqtt saying it could not reach the hardware. So barring hardware failure, the most common issue being the path.
Hence the checks that people is proposing here as the 1st step.

Now, what does the management web interface say?

1 Like
14

Thank you all for the good feedback!
I just came home and have tried to get it working.
I tried disconnecting/reconnecting the MR4 a few times with no success.
Then I moved it to another PoE connector, and now it seems to be working just fine!
It took a while for it to get in touch with everything (130 devices), due to rebuilding the mesh I guess, but that’s ok.
The only difference between the two PoE’s as far as I know, is that the one that works has an active power supply, and the other only has pass-through power supply.
Maybe the passive one didn’t have enough power to keep the controller running in a stable way.
If the controller is stable for a few weeks, I’ll replace the passive one with an active one, since that one is in a better location for reaching all the devices in the house.

15

The SLZB-MR4U supports active Power over Ethernet only (Active PoE, IEEE 802.3af) at 48V. It wont work correctly when connected to passive Power over Ethernet (Passive PoE).

Active PoE negotiates the proper voltage between the power supply equipment (PSE) and the PoE powered (PD) device preventing any potential damage to a non-PoE device.

Passive PoE is always on which may burn out the terminal devices if they’re not prepared for electrified Ethernet cables. Hence you should never connect computers and other non-PoE devices to a passive PoE switch!