Won't drain

What has happen is your drain line has become plugged with either rice or corn. Remove the drain line at the pump, you will also have to remove the hard line from the pump is self, (you will need a set of pliers to do so.) In side the hard line you will find a diaphragm with the cal pert to your problem, remove the blockage, check o-rings on the hard line to ensure that there is no cracks or breaks to prevent leaks. Tighten hard line back into the pump, and replace the drain line.
Hopefully this helps you out.