FLashing start/stop button?

Hi I have a Zanussi aquacycle FLE1115 W. When I switch on I can set all the functions as normal but the start/stop switch just flashes and will not start. I read somewhere about a diagnostic of pressing start and pause then switch on. I tried this and all the lights flashed one by one green except the drainage light which was orange. I have cleaned the filter and tried to completely drain the waste pipe of water. However, it still won't start the drainage light (in diagnostic mode) is still orange. What do I need to do to clear the fault please?