KD12DSS-2 error 3?

I load dishwasher, all correctly positioned, put the tablet in the dispenser...select ANY of the 6 programmes, and start.. Machine makes the filling up with water sound, then quite, nothing, no washing, no rinsing, just silence. Pause and open to see whats happening. The tablet has been released into the unit, but everything is dry and dirty and the tablet is in the unit unused. so nothing happens when i wash my dishes. if i let the cycle run its full cycle, an "err3" code comes up. what can i do to fix this