Blade will not turn

Somewhere deep inside on the shaft will be a shear pin.

Check the power supply: Ensure that the food processor is properly plugged into a functioning power outlet. Sometimes, a loose connection or a tripped circuit breaker can cause power issues.

Safety interlock system: The Kenwood Multipro 910 food processor usually has a safety interlock system that ensures all parts are properly assembled before it can start. Check if all the components, such as the bowl, lid, and blade, are correctly locked into place. If any of the parts are not properly assembled, the food processor may not work.

Motor overload protection: If you have been using the food processor for an extended period or with heavy ingredients, the motor may have overheated and triggered the overload protection mechanism. In this case, you will need to allow the motor to cool down for some time before it can restart.

Fuse or circuit breaker: Some food processors have a built-in fuse or circuit breaker that protects the motor from electrical surges. Check if your food processor has a fuse and ensure that it is intact. If it has a circuit breaker, reset it if necessary.

Mechanical issues: If none of the above steps resolve the problem, there might be a mechanical issue with the food processor. It could be a faulty motor, broken wiring, or a malfunctioning switch. In such cases, it is advisable to contact the Kenwood customer support or take the appliance to an authorized service center for repair.

call in an electrician as it may be the start/run capacitor for the motor ( indicated by motor humming but not running)
the gearing will make it very difficult to turn the blades by hand as the motor will be spinning at either 1400 rpms or 2400 rpms down to around 50 rpms for the blades

My Bamix stopped working--no shaft movement and loud motor noise (think disuse caused motor lubricant to thicken). Propped it upside down and put drops of quality machine oil at seam where narrow blade shaft enters larger shaft (in center of curved guard). Probably not necessary, but added a few drops where large shaft enters handle. Oil slowly seeps in. Attached a blade to manually turn for oil distribution. Did this periodically over several hrs. Turned on low speed and it gradually returned to full speed capacity.

Most motors of that type have a capacitor that puts the stator out of phase with the rotor. They are capacitor start induction run motors. These also have a centrifugal switch inside near the end ot the shaft to put power to the start winding for a split second to determine the direction of turn and to increase horsepower until it is up to speed. So if it fails to start either the centrifugal switch needs cleaning (or replacement if damaged) or the capacitor needs replacing to give it its original power, or the start winding has failed from overheating. There may be a thermal cutout on the start winding that may need to be replaced if it did overheat. If the start winding burned then the motor would require rewinding or replacement.

It sounds like your problem may be with the motor itself rather than the planetary, or with the board the motor switch is attached to. I think you need to test whether the motor is getting power when the switch is moved on. if it is, the motor may need to be replaced. If the switch is faulty, replace the board the switch is attached to.

Make sure your Beater can slip in and out of the Beater Shaft
easily. Do not force the beater onto the Shaft if the shaft is bent.
If it cannot be removed easily by hand, use a soft rubber mallet
(not a steel hammer) to slightly tap the beater so it can be moved
up and down the shaft or from side to side. Then you can easily
turn the beater left and remove it from the shaft.

From Kitchenaid Manual:
To Attach Flat Beater, Wire Whip, or Dough Hook
1. Turn speed control to OFF.
2. Unplug stand mixer or disconnect power.
3. Tilt motor head back.
4. Slip beater onto beater shaft and press upward
as far as possible.
5. Turn beater to right, hooking beater over pin on shaft.
6. Plug into a grounded 3 prong outlet.

To Remove Flat Beater, Wire Whip or Dough Hook
1. Turn speed control to OFF.
2. Unplug stand mixer or disconnect power.
3. Tilt motor head back.
4. Press beater upward as far as possible and turn left.
5. Pull beater from beater shaft

If the blade is locking in correctly and not loose then that is how it is supposed to be. Remove blade and reseat it to be sure.

Try to push up while you turn the blade. Don't be afraiid to turn hard.

click on the "contact" link in this website http://www.bamix-usa.com/ there's places in Canada & the US to have them serviced. Through contacting them they'll give you the nearest service area.
Good luck, love my Bamix!