When the machine is ready to spin it only hums. Belt is OK. I'm wondering if the clutch is constantly engaged. I don't believe there is power to the motor yet. You can turn the belt and the drum turns but appears to be tight. Should the drum turn when the belt is turned. Is there a clutch?
Depending on make and model it could be a broken belt.
You have a loose or torn band. The washing machine you describe( a top loader) has a band that pulls the "tub" that is why it is not spinning... Call a repair man or open it up and replace the part yourself. Check out a repair website.....