A power supply failure, bad outlet cord or a failed On/Off switch can prevent the sewing machine from powering up.
Check the power supply first. Plug a lamp or other small appliance into the electrical outlet that you're using for the sewing machine to make sure the outlet works. If the electrical outlet is dead, reset the house circuit breaker for the outlet. If the outlet still doesn't work, try using a different outlet to power the sewing machine.
If the electrical outlet is okay, unplug the sewing machine and check the outlet cord for damage. Replace the cord if it's damaged.
If the outlet cord is okay, check the On/Off switch for continuity using a multimeter (with the sewing machine still unplugged). With the switch turned to the 'on' position, the meter should measure near 0 ohms of resistance through the On/Off switch. If the meter measures infinite resistance, replace the On/Off switch because it's preventing the sewing machine from getting power.