Does it have an air operated water level sensor?
These are usually a small round unit with wires attached, and there's a small hose (around 8 mm OD) which goes from it to the bowl.
If it's got one, there's a possibility it's faulty or there's an air-lock in the hose.
Air locks can happen if the machine is tilted over or laid on its back (especially when transporting).
Pull the hose off the bowl end and blow gently into it. You should hear the sensor click, blow a little harder and it should click a second time.
Fit the hose back to the bowl.
Check operation of the machine. If it still overflows, the sensor is most likely faulty.