Why my macbook is locked?

[rain1007ht]

Yesterday I woke up and saw a screen asking for a six-digit PIN to unlock.
I called the support center and was directed to go to Find My Phone and press the Unlock button, but I don't see any Unlock button. My local apple support staff (Vietnam) also don't know why there is no Unlock button.
My machine:

• Macbook pro 2018.
• macOS 11.6.1.
• Logged in with my icloud account (with 2-step authentication enabled).
• Auto-update is enabled.

Can someone tell me what kind of lock this is and how to unlock? Thank you!

 

[tensixturtle]

Can you try these steps from the Apple Support page on a desktop computer?

Recover the passcode and unlock your Mac​

1. In Find My iPhone on iCloud.com, click All Devices, then select the Mac that’s locked.
   If you don’t see All Devices, it’s because you’ve already selected a device. Click the name of the current device in the center of the toolbar to access the Devices list, then select a new device.
2. Click Unlock, then follow the onscreen instructions to verify your identity with your Apple ID password.
3. Once you have your passcode, enter it on your Mac.