Agitator, impeller or front-loader?
A traditional top-loader has a tall agitator in the centre of the tub that twists back and forth. A high-efficiency top-loader has a low impeller plate instead, which moves the load by circulating water and clothing. A front-loader has neither — it tumbles the load using paddles as the drum rotates.
The phrase 'not agitating' means something different in each case, and each has its own set of likely causes.