It's done.
I had to manually enter the meter MPAN / MPRN numbers because they could not pick them up, but it's done now.
This might have been the issue with BG: They had the wrong postcode for the flat.
It was previously an office building, that's been demolished. It had a postcode.
The new-build flats all got new postcodes.
But when I bought the place and simply took over the supply from the incumbent supplier BG, I could not register an account with the new postcode. I had to use the old one. They had not updated their postcode database. And so it has been ever since; I have the wrong old postcode with BG. There's no way to fix that, AFAIK.
This might be at the root of their woes.
I suspect that when they 'updated' their system, they picked up a new postcode database, and now Things Didn't Match.
But they have no staff who can fix that.
It's off-script for the call-centre staff, and they have no-one they can escalate to. There is no second-level support.
All they can do is drop out of the bottom of their script with an "else: Our engineers are working diligently to resolve the issue!", which they know is bollocks; there are no engineers.
The company doesn't care; it's not a major dent in their revenue, and it only marginally increases the churn.
They might get paid incentives to install the smart meters, but they don't care if they work or not, that's not incentivised.
Having to read the things is a cost to the customer, not the company.
Anyways, Octopus now have the correct postcode and MPAN / MPRN numbers.