The drain pump cover does not engage properly.
Turn off the dishwasher.
Press the catch of the drain pump cover inward (1).
Tip the cover inward until it is released (2).
Rinse the cover thoroughly under running water and remove any foreign objects.
The drain pump (see arrow) is underneath the cover.
Carefully remove any foreign objects from the drain pump.
Check the drain pump impeller by manually turning it. You will feel a little resistance when you turn the impeller.
Reinstall the cover by pushing down.
Ensure that the catch engages correctly.