My problem is when I restart my MAC the USB keyboard doesn't work, I have been using this computer for a few years and this problem just started.
Mac Pro, OS X Yosemite (10.10.5)
If your wireless or USB keyboard doesn't work
Restart the computer holding down the command - option/alt - P - R keys before the gray screen appears. Continue to hold until you hear the startup chime for the second time.
Thanks, I tried this twice, the second time while on the phone with Apple support. I had read in other user comments that this problem may have been the results of the latest security upgrade. They couldn't help me either. I tested my keyboard on my laptop and it worked, I was about to use the USB ports with my scanner and my external hard drive and no problems there. It just didn't like my keyboard.
My solution was to upgrade to OS El Capitan and the keyboard is working fine.
Thank you for your assistance.
usb keyboard
