Enter your system lock PIN code to unlock this MAC after up date

Hello and welcome to Apple Support Communities,

What you are describing referes to your Mac's Firmware password, I'm guessing you must have set it in the past, I'm not referring to your user login password.

If you cannot remember it, an Apple Service Provider has the ability to unlock your mac's firmware password for you.

I hope this helps you.

Regards,

Peter.

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