Sometimes the water pump can stick slightly which will stop it from turning. This is especially the case with new motors as the rotors can stick until run in. Also units which have been left standing for a period of time can have some corrosion that resists the motor turning.
It is often possible to quickly and simply restore the operation of the pump without any disassembly or specialist tools required.
Simply unscrew the lid of the water tank and you will see that the impeller housing can be accessed. Use a small screw driver or other implement such as a paper clip to rotate the impeller a few times.
Switch the pump back on and if it still does not spin turn off and repeat the process.
If after a few attempts the motor does not start to spin you may require a replacement in which case contact customer support.