When your stand mixer doesn't run, the problem could be a lack of electrical power, broken wires, a failed motor or control problems.
First, check the outlet's GCFI breaker and reset it if it's tripped. If the GCFI is fine, see if the stand mixer runs when you plug it into an electrical outlet on a different circuit. If not, check the house circuit breaker for the dead outlet and reset if it tripped.
If the mixer won't work when plugged into a working electrical outlet, unplug the mixer and check the power cord. Replace the cord if it's cut or damaged.
If the power cord is intact, check the cord's wiring connections on the speed control plate or electronic control board. Reconnect any loose power cord wires and repair any broken power cord wires.
If the control wiring connections are okay, check the carbon motor brushes (with the mixer still unplugged). Replace both carbon brushes if either carbon brush is worn down shorter than 5/16-inch.
If the motor buzzes but doesn't spin, and the motor brushes are both okay, then you most likely need to replace the motor because the motor windings are bad.
If you haven't figured out why the mixer won't run after following these tips, other possible causes are a failed speed control plate, phase control board, or electronic control board, or a tripped motor overload switch.