Hi.
That means that the drain hose is blocked.
check first the drain hose at the back, see if it is free, and ensure it is not kinked.
If that does not fix the problem you will need to access the drain pump, undo the drain pump hose, and remove blockage in there.
The drain pump is located at the bottom side, toward the bottom of the machine. The pump is accessed opening the service panel at the back of the machine.
Once pump is located disconnect the drain hose from pump and remove blockage.
Keep a container ready to collect water when you undo the pump.
Appliance must be disconnected from power before starting.
Pump is part number 15 on the diagram below, please click on the picture to enlarge:
If there is no blockage, then it can be a defective pump, a wiring problem, or a defective pressure switch. Usually unclogging the hose will fix the problem.
Regards.