Sounds sarcastic but make sure the power point is OK. If you have checked everything you said plug, lead, switch, wiring and brushes then the only thing left is the motor field coils of the armature. One of these is open circuit. That is a winding has broken. Some you can see and or smell but otherwise a circuit tester is your only friend. If you find that one of these is at fault then the unit is probably not worth repairing. Cheers Bob