The coffee beans may not be fresh.
How to tell if the beans are fresh:
Coffee beans are very elastic. To see if your coffee beans are fresh bounce one on the floor. If it bounces the coffee is good. If you are using ground coffee pour a teaspoon of it into an already filled cup of water. If it floats the coffee is good.
Fresh coffee beans or freshly ground, high quality coffee are the most important ingredients in making a great tasting drink.
For a wide selection of coffee beans hand picked by De'longhi to help you get the best out of your machine please see the following link.
Once your coffee is opened it will start to lose its freshness rapidly, we recommend it is stored in an airtight container.