I have the HomeAssistant green with the USB thread border router set up. I have been using it successfully for a few weeks running a number of Arre temperature/humidity sensors, an Aqara motion sensor and, more recently, an Onvis smart plug.
Until to-day, the only problem that I had after I had configured it in the first place was that the motion sensor (in my shed) was a bit far from the house and would often go unavailable. I solved that by adding the smart plug in the conservatory, which acted as a relay, and the shed sensor was then very reliable. Very occasionally, devices would drop out for a short period, but they would usually come back online again after only a brief break.
This afternoon, I installed quite a number of Aqara door/window sensors on my various windows. These are Matter over Thread devices. They worked well when I set them up and all worked well for about 4-5 hours, but then suddenly I noticed that quite a number of Thread devices had become unavailable, including some (but not all) of the new sensors that I added, some (but not all) of the existing temperature/humidity sensors, the smart plug and the motion sensor.
I tried restarting HomeAssistant, but this was not successful. I do not know how to go about troubleshooting this and should be grateful for any assistance. Thank you.
Not sure if this is the case here, but Onvis Smart plugs might come with a firmware that has a critical bug.
The bug will prevent relaying in the Matter fabric.
You need to check for updates to the plug and Onvis require an Apple Matter hub to acheive that and it needs to be done in their Onvis app.
And regarding your Onvis plug, then find a way to update it.
I had to buy an Apple Minipod Mini update my plugs and then return it.
Let us just say that Onvis is not on my recommended list anymore and I go out of the way to warn against it as long as they do not have a general update method available.
The one they have is also quite convoluted, so even with an Apple Matter hub it is not just straight forward.
However the update do improve the Matter network a lot, so it is really needed to do, and the bug not only affect the Onvis plug, but the entire Matter network.
It might be the updated firmware, but you can not test it in HA, because Onvis do not use the CSA DCL where updates are officially published.
You have to search the Onvis pages, both website, Facebook and forum to find the announcement, and then check the versions.