Matter error code 3 means the accessory still believes it belongs to a fabric — yours, a previous owner’s, or a half-finished attempt in another app. The device refuses a new commission until that membership clears.
Find the owning fabric
Check every controller you ever used: Apple Home, Google Home, SmartThings, Alexa, Home Assistant. Look for gray devices or duplicate names. Ask household members if they paired it to a different home. Vendor apps sometimes show cloud binding even when Matter failed locally.
Clear error 3 properly
Delete the device from the app that originally commissioned it. If unknown, remove from all apps. Run the manufacturer factory reset (button hold per manual). Wait two minutes powered, then recommission from one primary controller only. Do not scan QR codes with multiple apps open. For used gear, assume prior fabric — reset is mandatory.
Verify
Pairing proceeds past error 3. Toggle works in primary app ten minutes later without reappearing as already added.