Thread runs on IPv6 under the hood. Routers with IPv6 disabled, broken, or filtered often still serve fine Wi-Fi — then Thread discovery times out, Matter-over-Thread commissioning never sees accessories, and support forums blame the bulb.

Confirm IPv6 is the blocker

Thread fails while 2.4 GHz Wi-Fi Matter devices pair. Border router shows connected in its app but Thread children never appear. ISP gateway has IPv6 off or LAN IPv6 unsupported in admin UI. Same hardware worked on a previous router that had IPv6 enabled.

Fixes homeowners can try

Enable IPv6 on the router if the ISP provides it — DHCPv6-PD or SLAAC per vendor docs. Reboot border routers after enabling. If ISP lacks IPv6, add an internal router that supports IPv6 ULA for LAN-only Thread per OpenThread guidance, or concentrate Thread on hubs that document offline Thread operation (Apple Home, Google Home) while you fix WAN IPv6. Disable guest isolation blocking multicast between phone and hub during setup. Update hub firmware after network changes.

When to stop

Corporate or ISP policies forbidding IPv6 need a network admin, not accessory resets.

Verify

Discovery should complete within minutes for a Thread device next to the border router. Accessories stay visible after phone reboot.

Official sources