I agree with all Fraser's suggestions. If the tank can't fill as fast as what fluid is being removed then you'll have a problem. Also check the level in the tank is correct once you've established that the flow into it is sufficient.
WE use a central water supply. The other machines are working good. I checked the inlet water pressure which is also good. I replace the pressure regulator, the INVA and FLVA. But also samedi situation.
If you are getting an insufficient water supply constantly or intermittently and the water level in the tank is correct then the level switch in the tank or the FM CPU board is faulty.
If the water pressure into the machine is correct but the level in the tank is low, INVA is open, then you have a problem with the float valve in the tank or something is restricting water coming though in to the tank.
just out of interest, where are you based Maxence11?
Do something for me Maxence, remove the stirrer to access the silver slotted screw on the float valve then remove that slotted screw. Put the stirrer back in then switch the machine on. The float valve will not be able regulate the tank level so you should get a high level, the float switch will close INVA to stop the tank overflowing and you should not get the low level alarm.
let me know what happens