Diagnosis
Incomplete draining. This is almost always a clog in the drainage path, starting with the filter and drain hose. The pump might be running, but it can't move the water past an obstruction.
How to Fix It
Remove the bottom rack and take out the filter assembly. Clear any debris from the filter cup and the chamber underneath. Next, check where the drain hose connects to the sink drain or garbage disposal. Disconnect it and make sure it's not kinked or clogged with gunk. You can also try pouring a cup of hot water mixed with a little baking soda down the drain hose to clear mild buildup.
If That Didn't Work
The drain pump itself could be clogged or failing. You'd need to access the pump, which is behind the lower front access panel. Check for a small object jammed in the pump impeller. If the impeller spins freely by hand but the pump makes a weak humming noise when it should be draining, the pump motor is likely dead.
Heads Up
If your dishwasher drains into a garbage disposal, always run the disposal for a few seconds before starting the dishwasher. A clogged disposal inlet will back water up into the dishwasher hose. Also, ensure the drain hose is looped up high under the sink to prevent sink water from siphoning back in.