You might want to consider starting a new discussion. Since this one is a couple of years old, less people are likely to look at it. You can link to this one. Post in the ElCapitan community.
If your wireless or USB keyboard doesn't work
Keyboard/Mouse – Troubleshooting Wireless
Reset an Apple Wireless Bluetooth Keyboard, Mouse or Trackpad (Troubleshooting Pairing and Other Common Problems)
Bluetooth devices become unresponsive
Bluetooth Interference Sources
Bluetooth Interference Sources (2)
Bluetooth Quick Assist
Bluetooth Wireless Problems
If your Wi-Fi is capable of generating a 5 GHz signal, try that.
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.
Reset NVRAM/PRAM