The ICE FULL and ADD WATER light flashes. What could be causing the issue?

Switch the unit off then push the water box to swivel all the way to the back. (NB Unit MUST be off). Switch unit on and off 2 – 3 times to recalibrate the unit.
The limit switch could be faulty and will need to be replaced.
The water box motor could be faulty and will need to be replaced.