The milk container is dirty.
Follow the step-by-step guide:
To prepare a number of cappuccinos and milk based coffees, clean the milk container after you have prepared the last beverage only. To proceed with making the next beverages, when the "Clean" message is displayed, press "Cancel".
If you do not clean the milk container the B8 symbol is displayed to remind you that cleaning is required.
The milk container can be kept in the refrigerator.
In some cases, to clean you must wait for the appliance to heat up.
To ensure correct cleaning, wait for the CLEAN function to end. You can, however, interrupt cleaning the milk container by pressing "Stop".
You do not need to empty it.
Hot water and steam are delivered from the milk spout. Cleaning stops automatically.