Hello everyone,
I’m hoping someone can help identify whether I’m dealing with a Home Assistant bug, an Inovelli firmware issue, or something else in the Matter commissioning process.
Hardware
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Home Assistant Green
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Home Assistant Connect ZBT-2
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Home Assistant Core 2026.7.1
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Supervisor 2026.06.2
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Home Assistant OS 18.1
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Frontend 20260624.4
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Matter Server 9.0.4
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OpenThread Border Router 3.0.1
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Verizon G3100 router
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iPhone (Home Assistant Companion App)
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Inovelli White Series Smart Dimmer
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Model: VTM31-SN
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Matter over Thread
Thread Configuration
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Preferred Thread network exists:
- ha-thread-ff59
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One Home Assistant OpenThread Border Router
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Thread integration shows healthy
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Matter integration is healthy
Matter-over-Wi-Fi devices are already working correctly (21 Matter devices currently connected, all Kasa Matter/Wi-Fi devices).
Problem
I cannot commission any of my Inovelli White Series dimmers.
I currently have seven VTM31-SN switches installed, and I have attempted commissioning on several of them.
Every one fails identically.
Commissioning Process
For every attempt:
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Factory reset the switch immediately before pairing.
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LED bar pulses blue throughout commissioning.
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Using the Home Assistant Companion App on iPhone.
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Home Assistant → Add Device → Add Matter Device.
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Scan QR code.
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iPhone recognizes the device as a Matter Light.
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Home Assistant requests permission to add the accessory.
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Commissioning begins (“Setting Up…”).
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Approximately 39 seconds later, commissioning fails with:
Unable to Add Accessory
Pairing Failed
The LED continues pulsing blue after failure.
Troubleshooting Already Performed
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Factory reset multiple switches.
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Attempted commissioning on several different switches.
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Replaced the original ZBT-2 with a brand-new ZBT-2.
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Recreated Thread network.
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Verified OpenThread Border Router is running.
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Verified Matter Server is running.
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Verified Thread preferred network exists.
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Verified Matter integration.
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Verified Thread integration.
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Verified switch is in Dimmer Mode.
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Verified Single Pole Mode.
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Tried iPhone on both 2.4 GHz and 5 GHz Wi-Fi (same result).
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Home Assistant and iPhone are on the same LAN.
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No Apple HomePod or Apple TV Thread Border Router exists on the network.
Home Assistant Logs
The log consistently reports:
Unexpected exception: 4
Unexpected exception: 5
Unexpected exception: 6
Expanding the traceback shows:
Logger: homeassistant.components.matter
Source: components/matter/_init_.py:320
KeyError: 4
File “/usr/src/homeassistant/homeassistant/components/matter/adapter.py”, line 73, in endpoint_added_callback
self._setup_endpoint(node.endpoints[data[“endpoint_id”]])
The traceback appears to indicate that Home Assistant receives an endpoint-added event but then raises a KeyError while attempting to access endpoint 4.
My Question
Has anyone seen this before with the Inovelli White Series (VTM31-SN)?
Specifically:
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Is this a known Home Assistant Matter bug?
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Is this a known firmware issue with the VTM31-SN?
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Does anyone know why endpoint_added_callback would generate a KeyError during commissioning?
Any suggestions or debugging ideas would be greatly appreciated.
Thank you!
