Since we had smart meters installed for gas and electricity last year, we have lost the electricity readings on my IHD twice. The engineer came round and replaced the electricity meter a couple of weeks ago, but the electricity readings stopped again after a few days. OVO have said that it is a firmware problem in the IHD, and a replacement will be rolled out after January.
Wondering if the IHD can be reset to temporarily fix the problem, I pressed the on/off switch and disconnected the charger (My IHD seems to have a battery in it so it works when disconnected from the supply). I then held the on/off switch pressed for some time while reconnecting the charger.
The IHD came up in a reset condition and reconnected to both meters after a minute or two. It is now showing both gas and electricity readings again. So if it fails in a few days, which I expect, I now know how to get it working again. I presume that there is some sort of software overflow problem which works for a time from reset and then fails. It would be interesting to know if this works for others having similar problems. The unit is a Chameleon and it says "type 2" and "IHD3-PPMID / CA30111" underneath.