Rock Pi 4C+ - Fan not turning on


I just received my Rock Pi 4C+ and the fan will not turn on. I’m using a USB-C power supply rated for 3.5A at 5.1v, for just under 18 watts.
I have the Fan plugged into PIN’s 2,4 and 6. The green light comes on but the fan does not.
Is there a setting I’m missing?