The inside of the appliance is very dirty.
If the message is still displayed after cleaning, contact a service centre.
The following parts of the machine must be cleaned regularly:
coffee grounds container (A13),
drip tray (A12),
water tank (A18),
coffee spouts (A8),
pre-ground coffee funnel (A2),
infuser (A17), accessible after opening the service door (A16),
touch screen (B)