My smart meter barely works - occasionally (once every few weeks) it's able to squeeze out a reading onto my Octopus account, but most of the time it's just "no data available". It seems to save up the data for a week or so, but the connection only succeeds every couple of weeks, so it's very intermittent and gappy.
I'm in one of the problem areas that doesn't use a mobile network for smart meter readings, so I presume it's signal issues. Family members are on the other side of the divide and have perfect working meters using the cellular network. There is probably a non-technical reason why they needlessly split the country in two like this - two companies both "owed" contracts for some favour or other by the last government.
I used to contact Octopus every so often, but the only response was always to send yet another bloke round to have a look, which invariably involved turning my power off for ten minutes to poke around and no fix. Sometimes, it was the same bloke again - I got tired of waiting in for blokes and the power disruptions and now just send meter readings to them old-style.