dark gulch
I will re-detail the basics, but please see https://discord.com/channels/330944238910963714/1373687628561383514.
About two (three?) weeks ago, all my Matter over Thread devices stopped responding. I initially assumed that one of my Inovelli white switches needed a reboot, so I air-gapped the one that I assumed was not responding. This didn't fix the unresponsive device. It was then that I checked in Home Assistant to discover that all my Matter devices were not responding.
I rebooted Home Assistant, and that did not resolve the issue. Followed by a number of troubleshooting steps, including spinning up a new instance of HA, resetting all my Matter devices, and resetting my Thread network by resetting all my Apple TBRs to factory.
Matter over Thread devices are now back on HomeKit, but they can not be added to Home Assistant, either via sharing from HomeKit or as a "new" device. I've attached my most recent log files.