Gotcha.
Couple of options here. Firstly, try using https://smart-meter-help.ovoenergy.com to make sure the meter itself is still communicating. If that checks out, ask OVO Support to run the XJoin command as it usually forces your IHD to re-pair itself with the meters and can fix some of these issues.
We’re limited in how much we can help with Digital Voice stuff here, but I’m happy to discuss that one as it’s related to the current thread. Long story short, the residential version shouldn’t impact your IHD as it cuts off at the router where you then plug in your usual phone that you would have used previously.
When it comes to the answerphone… That should restore soon but it apparently takes a few days to migrate over and can’t be done until after the line itself has migrated. You should talk to BT if it still doesn’t restore by the end of this week.
It’s a mandatory migration though, as Openreach is turning off the old telephone infrastructure (PSTN) in January 2027 - if you upgrade your broadband to Fibre or Full-Fibre, doing this migration to DV is a requirement if you still want phone service.