Alright, sharing this in case it helps someone else from pulling their hair out like I did 
So I recently got a new Thread-enabled sensor (the Aqara one, in case you’re wondering), super excited to add it to my Matter setup. But man, getting it to actually connect was a mini nightmare.
At first, it just wouldn’t show up in the Matter hub (I’m using Apple Home via my Apple TV as the hub). I reset, re-paired, rebooted—nothing. Then I realized the hub and the Thread Border Router weren’t properly synced. I assumed since Apple TV supports Thread, I was good to go, but turns out you really need to make sure it’s the 4K version (second-gen or later) and that it’s updated.
Also, my phone was on 5GHz Wi-Fi while the Apple TV was on 2.4GHz—crazy enough, that messed things up too. Once I put both on the same band, boom, device finally showed up in the Matter onboarding.
Moral of the story: double-check that your hub is truly Thread-capable and up-to-date, make sure all devices are on the same network segment, and don’t assume factory reset always fixes it (sometimes it’s just a network mismatch).
Anyone else hit this wall? Or got smoother ways to pair Thread devices with Matter? Would love to hear them!