First thing is to assume you have a defective board, but lets check a few things first because you could have an intermitent issue with the draining and it was just a coincidince it worked with the old board installed.
Put the new board back in and press the "cancel/off" button which should turn on the drain pump.
Does the pump run? If not, is there power to the pump and maybe its not running because the impeller is jammed up? If thats the case, you will usually feel a slight vibration or a quiet humming noise from the drain pump if it has power but the impeller is unable to turn.
If the pump is not running, or its not trying to run, did you pull on any wiring or partially unplug the pump when you were changing the element? Make sure the pump is plugged in.
If the pump is running but water is not draining its likely you have a restriction in the drain line somewhere. Some things stuck in the hose or air gap can cause the dishwasher to drain one time and not another.