imac not recognizing usb keyboard

I have an imac and I use the usb keyboard because I like the number pad on the side. I tried to plug something into the usb port on the side of the keyboard and now the keyboard isn't working at all. If I disconnect the keyboard, it works on my macbook, but it doesn't register with the imac. I unplugged the machine, because I couldn't log off without a keyboard due to multiple users, and restarted, now it's just searching for a bluetooth keyboard, It doesn't see that the usb keyboard is plugged in. This has been a repeated problem, I'm usually able to fix with a restart, but this time it's not working. Thanks