Check that you are using the right cups for the diameter of the fruit you want to squeeze. You also have to check that the balls are well screwed in. Restart the machine and allow 10 minutes to pass; if the error persists, contact Zummo Technical Support.
Check the machine’s fuse and make sure it is still working. If it is not working, you should change the fuse. You can change it yourself following the instructions in this video. If the machine still does not work, contact the Zummo service.