filament_motion_sensor on Flsun V400 / MKS Nano V2.0

[The-Padi]

I have a problem with the filament_motion_sensor : It goes immediately into Filament encoder runout at the start of the print. I'm working with a FLSUN V400 with a MKS Nano V2.0 motherboard and here is the printer.cfg

[filament_motion_sensor encoder_sensor]
switch_pin: ^PA13
detection_length: 25
extruder: extruder
pause_on_runout: False
event_delay: 3.0
runout_gcode:
  PAUSE
  M117 Filament encoder runout
insert_gcode:
  M117 Filament encoder inserted

Can anyone give me a hand please ?