Shelly BLU H&T Display ZB (SBHT-103C): SYNC always fails, genTime returns UNSUPPORTED_ATTRIBUTE

What happened?

What happened?

The Shelly BLU H&T Display ZB cannot synchronize its clock via Zigbee2MQTT.

The device works correctly otherwise:

• Temperature updates
• Humidity updates
• Battery updates
• Device joins and communicates normally

However, when manually triggering clock synchronization on the device (SET -> SYNC), it always displays:

SYNC FAIL

Device

Model: Shelly BLU H&T Display ZB
Model ID: SBHT-103C

Firmware before update:
251118 / v1.1.9

Firmware after update:
260512 / v1.2.20

The firmware update was performed successfully using Shelly BLE Debug.

Zigbee2MQTT

Version: 2.12.1
Frontend: 2.12.0
zigbee-herdsman: 10.6.1
zigbee-herdsman-converters: 26.76.0

Coordinator:
Texas Instruments Z-Stack 3.x.0

Home Assistant

Home Assistant OS
Linux 6.18.37-haos

Investigation

The device exposes the genTime cluster.

Using the Zigbee2MQTT Dev Console:
Endpoint: 1
Cluster: genTime

Reading the "time" attribute returns:

Status: UNSUPPORTED_ATTRIBUTE

Other attributes under genTime also return unsupported.

Because of this, the device never synchronizes its internal clock and manual SYNC always results in "SYNC FAIL".

Expected behavior

The device should obtain the current time from the Zigbee Time cluster and display the correct local time.

Additional information

• Factory reset performed.
• Device removed and re-paired.
• Firmware updated to v1.2.20.
• Same result before and after firmware update.
• Zigbee communication is otherwise fully functional.

What did you expect to happen?

No response

How to reproduce it (minimal and precise)

No response

Zigbee2MQTT version

2.12.1

Adapter firmware version

20221226

Adapter

SMLIGHT SLZB-06 (CC2652P, Z-Stack 3.x.0)

Setup

Home Assistant OS add-on on Intel NUC.
Coordinator: SMLIGHT SLZB-06 over Ethernet.
MQTT: Mosquitto add-on.

Device database.db entry

No response

Debug log

No response

Notes

No response

Start by reproducing the failure in the Zigbee2MQTT Dev Console against endpoint 1 and the genTime cluster, confirming the time attribute still returns UNSUPPORTED_ATTRIBUTE. Determine whether the device can provide time through the existing Zigbee2MQTT integration, and consider the issue done when clock synchronization succeeds and the device displays the correct local time.