If a Mac OS X has issues related to settings stored in NVRAM, resetting it might help in restoring an application.
- Shut down your Mac.
- Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
- Turn on your Mac.
- Press and hold the Command, Option, P, R keys immediately after you hear the startup sound.
- Hold these keys until the computer restarts and you hear the startup sound for a second time.
- Release the keys.
Note: After resetting NVRAM, you may need to reconfigure settings for speaker volume, screen resolution, startup disk selection, and time zone information.
Once the keys are released, the NVRAM in Mac is reset and should function properly.