Are you saying that it will not count down to Zero?
Either the meter is jammed as in not turning or the probe is not sending the signal to the computer board.
Which meter is in use? the 3/4 turbine or the paddle wheel?
To check the sensor at the meter end take a magnate and pass it close over the end and check for flashing water drop, flashing means the wire is good and that the meter is jammed and needs to be cleared.