Reset NVRAM: To do that, turn off your Mac, then turn on, when you hear the start-up sound, press and hold the Command-Option-P-R keys.This article explains how to free up space on your Mac. Did you see any low disk space warnings before this problem? Your Mac should have at least 9 GB of free space. If your Mac can start up, the problem may be that your computer does not have enough space. To do this, turn on your Mac, when you hear the start-up sound, press and hold the Shift key until you see the Apple logo. I previously wrote an article about how to fix Mac startup problems.Wait a few seconds and then press the power button to turn on your computer.

Press and hold the power button for a few seconds until your computer turns off, then release the power button.Enter your admin password and then restart your Mac.Fix Mac OS X El Capitan Perform the steps below one-by-one until your problem resolves.While still on the safe mode, do the following steps: If it still doesn’t work, then maybe it’s time to use the terminal app that will lead you reverse the safe mode.Release the keys as soon as the computer has already started up.Hold down the keys until the computer starts up again and you hear the startup tone for the second time.Press the keys that the Options, Command, P and R keys simultaneously.Locate the Options, Command, P and R keys on the keyboard.It will only reset small setting, but it may help you resolve the issue of your Mac still being stuck in safe mode. Resetting this may mean changes for your time zone, sound volume, and etc. PRAM (Parameter Random Access Memory) stores your system setting. If there aren’t any problems with your shift key, then it’s time to reset your PRAM (or NVRAM).

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