Iíve had this happen several times on a Maytag PDB24330AWX dishwasher.
Sounds like a broken lifter. Itís attached to the solenoid mechanism, but is located inside the tub area. Here's a diagram
. Fortunately, you can get a lifter for $3 - $5. After shutting off power to the unit, open the door and unscrew the spray arm and remove. This can be done by hand. Then, unscrew the the three 'star' screws in the round drain cover. Underneath, you'll see an L-shaped, spring-loaded rod and a small, straight rod with a black, plastic; L-shaped piece attached to it. Most likely, the L-shaped piece...that's the lifter...will be cracked, chipped or broken. Remove the securing clip and pull it off the metal rod. Replacements are readily available from a Maytag dealer, or online. To replace it, start by re-attaching the solenoid bar to the retaining clip in the motor area (this is why we want the power off.) Using a lightweight c-clamp (or, I've used electrical tape), secure the solenoid in the 'down' position. Now, go back to the tub and slide the new lifter onto the rod onto the shorter, straight rod, while holding the spring-loaded rod in the 'up' position. You'll see that the lifter can only go on in one position. Once firmly in place, attach a new c-clip to the groove near the end of the metal rod (you'll see it). Now remove the clamp or tape from the solenoid, reattach the drain cover and wash arm and turn the power on. You should be good to go.
One more thingÖ.before you start, make sure that the solenoid plunger can easily slide back into the solenoid. Iíve seen solenoids overheat and close up. When that happens, the solenoid will also have to be replaced.