How to Reset NvRAM

1. Shut down the computer.
2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Immediately press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears. Continue holding the keys down until the computer restarts, and you hear the startup sound for the second time.
5. Release the keys.