The brew unit filter is blocked.
Clean the brew unit of the coffee machine once a week by hand.
Proceed as follows:
Disconnect the coffee machine from the mains.
Open the appliance door on the right-hand side of the coffee machine.
Press and hold the button at the bottom of the handle of the brew unit (1).
Whilst doing so, turn the handle to the left (2).
Carefully pull the brew unit out of the coffee machine.
Clean the brew unit by hand under warm running water without using any cleaning agent. The moving parts of the brew unit are lubricated. Cleaning agents will damage the brew unit.
Wipe any coffee grounds off the filters (see arrows).
Dry the funnel to prevent ground coffee sticking to it the next time a coffee is made.
Clean the inside of the coffee machine.
Use your vacuum cleaner to remove dry coffee residues from the coffee machine.
Slide the brew unit back into the coffee machine, ensuring it remains straight.
Press and hold the button at the bottom of the handle of the brew unit (1).
Whilst doing so, turn the handle to the right (2).
Close the appliance door.