Computer suddenly not recognize my keyboard

What troubleshooting have you tried so far? For example:

1. have you tried shutting down the computer and restarting?
2. have you tried unplugging and plugging in the keyboard
3. have you tried plugging it into another port?
4. have you tried using it with another computer?
5. have you tried plugging the mouse into the port where you had the keyboard? (to test if the port works)
6. if you are plugging the keyboard into a USB hub have you tried plugging it directly into the computer?