Apple USB Keyboard can't choose boot options

NB: Not about a bluetooth keyboard, I couldn't find any other category that seemed to be for just USB keyboards or keyboards in general.

I am unable to select boot options for my Mid 2010 iMac after buying an Apple USB Keyboard. Tapping the Alt key a couple of times or holding it doesn't make a difference. I've tried from a complete shutdown, and tried from a reboot. Connected directly to the computer, no other USB devices plugged into the keyboard, though there are other USB devices attached to the computer.