Thread experience

I bought a Wemo 247 Smart plug ages ago to have something that uses the Matter standard. At the time I was able to quickly add it to my Apple TV. Recently as the Matter integration has evolved, I thought I would try to add the smart plug to HA.

Removed it from Apple Home. Resetting the device was challenging, but eventually succeeded. I then went through a slow onboarding process in to HA. The device shows up as a HomeKit device even though I used the HA mobile app > device > add matter device option.

It does not show up in Apple home.

The response time was terrible though - it would typically take 30s to respond.

Today looking more closely at the above image I could see a Provision Preferred Threa… button. I pressed it and shortly after this the panel updated:

Changed to Router Eligible End Device.

Response time is now instant!!

BUT

The thread integration is still not showing anything:

After twenty minutes of instant response the Fan has disappeared!

All the entities are marked unavailable!

UPADATE:
Thought it might relate to distance from the HA server, so moved the plug, but two hours later it is still unavailable.

Any suggestions for resetting and a more successful pairing?