Look at the general advice for draining through the front filter. Make sure the pump-out can spin freely (no wire, coins etc in the rotating impeller. Put the filter back in.
NOW: on the ZWF1621 (and probably lots of others) turn off the machine. Press and hold the extra spin + start/pause buttons together, and turn the machine on. In this mode, error codes may display, and as you rotate the programme selector, various functions will kick in (water fill, pump out etc). Switch off for a while and next start, your machine should be reset and running.
ER, April 2010