How to Reset PRAM NVRAM on the MacBook Pro

Turn off your MacBook Pro computer.
Prepare to press the 'Command,' 'Option,' 'P' and 'R' keys. You will need to press all four of these keys in unison immediately before your MacBook completes its boot cycle.
Turn on your MacBook Pro.
Press and hold 'Command,' 'Option,' 'P' and 'R.' Your MacBook Pro will reset your PRAM and NVRAM, and will restart.
Continuing holding down the keys until you hear the Mac startup sound.
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