Fix Third Reality ZL1 pairing issues with ZHA

Symptoms

• Bulb never shows up during ZHA add/pair.
• Pairs once but drops offline shortly after.
• Shows as “interviewing” forever or “unknown” device.

Prerequisites

• Home Assistant up to date.
• Working Zigbee coordinator (USB stick or hub) on a short USB extension, away from the host.
• ZHA integration (not Zigbee2MQTT) for this guide.

Factory reset the ZL1 bulb

1. Power cycle sequence: turn power ON for 5 seconds, OFF for 5 seconds; repeat 5 times.
2. The bulb should blink to confirm reset and enter pairing mode automatically.

Put ZHA into pairing mode

1. In Home Assistant: Settings → Devices & Services → ZHA → Configure → Add device.
2. Keep the bulb powered within 2–3 meters of the coordinator for the first join.
3. Wait up to 3 minutes for interview to complete.

If it pairs but remains “interviewing” for more than ~5 minutes, cancel, power-cycle the bulb once, and try Add device again.

Avoid 2.4 GHz Wi‑Fi interference

• Set 2.4 GHz Wi‑Fi channel width to 20 MHz (not 40 MHz).
• Prefer Zigbee channels 15, 20, or 25 to reduce overlap with common Wi‑Fi channels.
• Reduce AP transmit power to Medium in dense deployments so the bulb prefers the nearest AP.
• If your router offers Wi‑Fi 6/6E Multi‑Link Operation (MLO), disable MLO for the 2.4 GHz SSID.

After it joins

• Rename the device and assign it to an Area.
• Let the device sit for a few minutes for clusters to finish initializing.
• Create a simple light.toggle in HA to verify control.

Troubleshooting checklist

• Move the bulb within 1–2 meters of the coordinator for first join, then relocate.
• Use a short, quality USB 2.0 extension to move the coordinator away from metal/EMI.
• Remove any half‑paired “ghost” entries (ZHA device list → the device → Remove).
• Power‑cycle the bulb and retry Add device.
• If still failing, pick a different Zigbee channel (15/20/25) and re‑pair after a full ZHA restart.

Further reading