The grounds container is dirty.
There will probably also be some water in the grounds container left over from the rinsing process.
Clean the grounds container daily to prevent unpleasant odours and mould from forming.
Open the coffee machine door.
Lift the grounds container slightly and remove it by pulling it to the front out of the coffee machine.
Empty and clean the grounds container in the dishwasher or by hand using warm water and a little washing-up liquid.
Dry the grounds container.
Ensure that grounds container insertion slot is thoroughly clean on the top right and top left (arrows).
The sensors can only properly detect the grounds container and whether it is soiled if the area around the sensors is clean.
Use a damp cloth to clean the insertion slot for the grounds container in the coffee machine.
Dry the insertion slot.
Push the grounds container back into the coffee machine and close the appliance door.
