Best answer by Tim_OVO
This sorted in the end,
Few suggestions for you and anyone else with the same issue: if the meters have recently been fitted, we might not have updated your account with the new details. This can take 4-6 weeks. This would mean that My OVO and the app wouldn't know you have smart meters, and would estimate your usage until this update is complete. Another possibility is a poor signal around the electricity meter area. This would mean we're not getting sent your readings, and the app would need to use estimates. With those details, I'll be able to check either way.
I've edited this topic so other users with the same query can find it more easily.