The grounds container is full.
Follow this step-by-step guide:
When removing the drip tray, the grounds container must be emptied, even if it contains few grounds. If this is not done, when you make the next coffees, the grounds container may fill up more than expected and clog the machine.
If you make a number of cappuccinos one after the other, the metal cup tray becomes hot. Wait for it to cool down before touching it and handle it from the front only.
This can be done using the spatula on the brush provided.