How to reset iCloud locked MacBook

If the question mark is persistent, and your Mac does not start up normally:

1. Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off.
2. Every Mac has a power button. On notebook computers that have Touch ID, press and hold Touch ID.
3. Use Disk Utility to repair your startup disk. Follow the steps for a Mac with an Intel processor.
4. If Disk Utility found no errors or repaired all errors, reinstall macOS.
5. If you still need help, please contact Apple Support.

Victortrrjojimenez Said:

"How to reset iCloud locked MacBook: I bought a Mac online and decided to erase it, to gain owner ship from previous owner who sold it to me. But now the computer just shows a folder and question mark , how can I factory reset it the rightful way How to reset , if the owner does not respond back ."

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Seems you've been scammed, though a full assumption on my part.

Avoiding a Scam Sale:

Next time you go about purchasing a used device, instruct the user to youse this site, including the iCloud logout: What to do Before you Sell, Give Away, or Trade In your Mac - Apple Support.  The seller should have known better. Prior to hand in the money, request that they let you log into your Apple ID on it. If the sell decides to disabide by those rules you've set forth, then do not proceed with the transaction.