It Could be the coupling but does the motor run when in spin ? Does the water get pumped out?
to gain access to the coupler the ENTIRE cabinet comes off. You need to pop out two S-shaped clips which are hidden under the top console . On the edges of console are a plastic trim which come off and then you'll see a screw holding the console to the top . Remove these screws and pull out and up and lay the console back and let it hang there. On each side are these clips - pop out whit a screwdriver. Unplug the 3 wire connector to the top. open lid and pull up and out and remove the entire cabinet ( front hooks under frame) Now remove the pump which is held on with two springy clips. Remove the two screws in the clips on motor and remove the two clips holding the motor. Now pull the motor straight out. Now you'll see the coupler - plastic piece, then rubber piece, then rubber piece on transmission shaft. These can go bad in a couple of ways - sometimes the hole gets egg shaped and slips on the shaft, plastic cracks, rubber piece breaks etc.