New group format - Unable to use state

Hello,

I was trying the ‘new’ group format for combining 2 sensors.
As far as I understand this is how it should be done:

platform: group

name: "Electricity Meter Energieverbruik Total"
unique_id: "group_electricity_meter_energieverbruik_total"
type: sum
unit_of_measurement: kWh
device_class: energy
state_class: total_increasing
ignore_non_numeric: false
entities:
  - sensor.electricity_meter_energieverbruik_tarief_1
  - sensor.electricity_meter_energieverbruik_tarief_2

But it gives me the following error in the logbook:

Logger: homeassistant.components.group.sensor
Bron: components/group/sensor.py:423
integratie: Groep (documentatie, problemen)
Eerst voorgekomen: 13:49:14 (5 gebeurtenissen)
Laatst gelogd: 14:58:41

Unable to use state. Only numerical states are supported, entity sensor.electricity_meter_energieverbruik_tarief_1 with value unavailable excluded from calculation in sensor.electricity_meter_energieverbruik_total
Unable to use state. Only numerical states are supported, entity sensor.electricity_meter_energieverbruik_tarief_2 with value unavailable excluded from calculation in sensor.electricity_meter_energieverbruik_total
Unable to use state. Only numerical states are supported, entity sensor.vaatwasser_yearly_energy_kwh with value unavailable excluded from calculation in sensor.household_yearly_energy_kwh
Unable to use state. Only numerical states are supported, entity sensor.wasmachine_yearly_energy_kwh with value unavailable excluded from calculation in sensor.household_yearly_energy_kwh
Unable to use state. Only numerical states are supported, entity sensor.wasdroger_yearly_energy_kwh with value unavailable excluded from calculation in sensor.household_yearly_energy_kwh

I do not know what is wrong or why it shows the error.

In develeper tools it has the correct calculated value.

I used to do this with a template instead of the group thing. Not sure which of the 2 is better to use.

Can anyone please explain me why i get this error?

because homeassistant is getting more and more a bug collection from my point of view.
currently this issue is back since 2024.11

after it has already been resolved 2023