Installation & TroubleshootingFor problems with Arduino itself, NOT your project
For problems with Arduino itself, NOT your project
Does your code include pinMode (pin13, OUTPUT); ?
N-Channel MOSFET (FDP8880)
You can prove the pin is turning itself off by disconnecting the motor and connecting a LED and resistor to the pin, set the pin to HIGH, and wait till the LED turns off on its own.
It's a Uno; there's already a LED there