what does F0 mean on fisher & paykel dishwasher?

I have a F&P Nautilus Dishwasher and it is driving me insane. I have had someone come to look at it but they told me to use powder not tablets which i have been however the same problem keeps arising. The dishwasher will stop part way through a cycle and sound like it is running, but its not doing anything. The digital screen is blank usually however on one occasion I happened to notice F0 come up momentarily. I regularly have to pull the dishwasher out and turn it off at the wall to stop it from "running". Sometimes it just beeps in the middle of the night for no apparent reason. Can anyone tell me what might be wrong, and how to fix. Or is all hope lost and I need to replace? Many thanks