The drain pump cover does not engage properly.
Switch the dishwasher off.
Press the catch of the drain pump cover inwards (1).
Tip the cover inwards until it is released (2).
Rinse the cover thoroughly under running water and remove all foreign objects.
The drain pump (see arrow) is underneath the cover.
Carefully remove all 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.
Refit the cover by placing it down vertically from above.
Ensure that the catch engages correctly.