If a washing machine does not spin, there may be either an electrical or a mechanical problem with its lid switch assembly. The motor coupler, which connects the motor to the washer's transmission, may also have failed. The latter scenario is particularly common if the washer has been overloaded.
A drive belt defect is another possible explanation for a washer's failure to spin. It is important that the drive belt be intact and tight on the washer's pulleys.
Failure to spin also results from defective door latches, which can fail either mechanically or electrically. The washer's motor control board should be checked as well.