My two Matter over Thread devices are no longer reachable through HA

I have a Nuki Smart Lock Pro 4.0 and a Matter door sensor by Aqara, both using Matter over Thread. This all worked perfectly fine for many months, until recently. I believe the disconnect occurred when upgrading to HA 2024.2, though I’m not sure if that’s the exact moment and/or if there’s some coincidence involved there.

The devices and their entities simply show up as unavailable.

I have three Nest Wifi Pros, which serve as the Thread border routers to make HA talk to the devices.

It’s worth noting that the Google Home app can still communicate with these devices.

Where should I start to fix this? I rebooted every part of the sequence (Nuki device, Nest Wifi Pro, and HA itself), but to no avail.

Are the thread and matter related addons running?
Are the thread and matter related integrations running?

Mine seems to fail with every host reboot and have to manually restarted.
It looks like the restart brings up the integrations before the addons are ready and then the integrations fail.
When I tell the integrations to reload, then the addons are up and running and everything just works after that, but I seem to always have to make that manual step with at least one of the integrations.

Hmmm, interesting: the Thread integration says “No devices or entities”. When clicking Configure, it does show my three Nest Wifi devices.

Restarting both the Thread and the Matter integration doesn’t make a difference. Same goes for the Matter add-on.

There might be both a thread and a thread border router in either addons or integrations.

Probably start with the Matter Server (AddOn) logs to see if is able to talk with these devices.