They usually have a fair sized hole from dispenser to drum, so for that to get blocked, If you can reach into draw unit, and get to outlet, poke some thing in, lenght of wire etc to free it, failing that, you would need to remove top, and then remove top of dispenser unit, to clear blockage, Only thing it is going to be blocked with is soap powder, So after clearing, you will have a fair bit of soap in the drum unit.
SD, August 2011