A failed power supply, broken power cord, tripped circuit breaker switch, failed circuit breaker switch, bad power switch, wiring failure, bad motor control board or failed console display can prevent the treadmill from powering up.
Make sure the electrical outlet the treadmill is plugged into has power by plugging a lamp or small appliance into the outlet to see if it works. If the outlet is dead, reset the house circuit breaker to restore power to the outlet. If the outlet still doesn't work, plug the treadmill into a different outlet and have an electrician repair the broken electrical outlet.
If the electrical outlet works, unplug the treadmill and check the power cord for damage. Replace the power cord if it's damaged. If the power cord is okay, check the circuit breaker switch on the treadmill and reset the circuit breaker switch if it's tripped.
If the circuit breaker switch isn't tripped or the treadmill won't power up after resetting the circuit breaker switch, use a multimeter to check for continuity through the circuit breaker switch (with the treadmill unplugged). Replace the circuit breaker switch if the meter measures no continuity.
If the meter measures continuity through the circuit breaker switch, check the power switch for continuity (with the treadmill still unplugged). Replace the power switch if the meter measures no continuity through the power switch with the power switch turned on.
If the power switch is okay, check all wires between the power cord connection and the motor control board. Reconnect any loose wires and repair any broken wires.
If wiring that connects power to the motor control board is okay, check the wiring between the motor control board and the console display. Replace any loose wires and repair any broken wires.
If wires between the motor control board and the display control board are okay, then a bad motor control board or a failed console display could be preventing the treadmill from powering up.