I know the solution.
I have also had this problem and it was nothing to do with a blocked pipe and also the pump on mine is working correctly.
It is to do with a dirty float switch stuck up/on.
It seems to work when the float switch is activated for a certain amount of time the alarm goes off and the flashing condenser full lights.
How to get to the switch is the biggest problem.
It is located behind the Right hand pannel as you look at the front of the machine.
Make sure you have the power off and unplugged before you start working on the machine.
You will need a Star driver and some vasaline(yes it is waterproof non-conductive greese).
You need to undo a number of screws on the back and also on the front also remove the top via 2x screws.
Once you have done this the pannel lifts up and out.
Behind the pannel.
At the bottom there is one more screw and you should be able to get to the float switch and the pump.
Clean the switch and greese. Check the microswitch is clicking on when pressed up and returning down to the off position.
I hope this helps someone
Jason