i have a diplomat adp8352,and water drains straight out?

I have a diplomat adp8352 and when the water enters the machine it drains straight out and then the machine stops and 2 red lights flash. I removed the machine to take a look and was able to start the machine (it went through a full cycle) by covering the drainage pipe when it started forcing the water back in. It still won't work if i dont do this, which isn't much help as i cannot refit back in to the kitchen. Anyone have any ideas on how to fix this?