Well if you press it and the lights come on then the main bar switch must be working.
Does the light in the bar come on when the hoover is reclined, and go off when its upright?
If so, then its more than likely the motor, and you will need to check that the motor is receiving power, for which you will need a multimeter, initially set on 500V AC, and put the probes on each terminal on the motor with the unit reclined and switched on.
You will be testing the voltage across the motor's terminals, so always assume its 240V Ac being supplied to the motor and be careful.
If the motor Is receiving the voltage, then the motor is faulty. If there is no voltage to the motor then the supply is faulty and you will have to determine why - it could be the driver PCB.
Either way, I'd test the motor is getting a voltage first.