what is wrong with candy G0482?

My Candy washing machine model GO482 has broken. When I start a cycle it fills with water then just stops at the point where the drum should start turning. I can still drain the water out on the drain cycle although the spin cycle doesnt work. I presume that because of this the pump is fine. I cleaned out the filter at the bottom of the machine and it isnt blocked by anything. Could it be something as simple as the belt pulley?