Missing data using ApexCharts vs Statistics-graph

Configuration Frontend
1

Hi I have this simple graph based on utility meter sensor. Works s expected

chart_type: bar
period: day
days_to_show: 7
type: statistics-graph
entities:
  - entity: sensor.daily_energy_production
    name: kWh / jour
stat_types: state

… resulting in this graph
image

Now I try to get the same with ApexCharts

type: custom:apexcharts-card
experimental:
  color_threshold: true
header:
  show: true
  title: Historique de production solaire
  show_states: true
  colorize_states: true
graph_span: 7d
span:
  start: day
  offset: '-6d'
show:
  last_updated: true
yaxis:
  - min: 0
    max: 50
    decimals: 0
    apex_config:
      tickAmount: 10
series:
  - entity: sensor.daily_energy_production
    name: Production par jour
    type: column
    show:
      datalabels: true
    min: 0
    max: 6
    transform: return Number(x) / 1000;
    unit: KWh
    group_by:
      func: max
      duration: 1d

… which gives me this
image

Any idea why I miss all data before Sept 12 ? While they are there with Statistics-graph.

Thanks, Bernard.

2 
series:
  - entity: sensor.daily_energy_production
    fill_raw: last