Can't unlock my macbook pro

Hi,

For a reason we dont understand, our Macbook pro ("Eugene's MacBook Pro",

Serial: C0***KQ1) goes after boot into disable mode and it says that in order to unlock it we should use the icloud 4-digits PIN from icloud.com/find.

When we login into icloud.com/find we can't see the device inside the 'all devices' list.

Due, we can see it in the settings. but we can't perform unlock or any other operation.

Also, we can't find the 4-digits PIN number to unlock it.

Currently the mac is stuck and we can't resolve the problem.

Is this a new Mac that you use everyday or a used Mac you just acquired?

Or there other devices involved?

What to do before you sell, give away, or trade in your ... - Apple Support

How to set a firmware password on your Mac - Apple Support

https://discussions.apple.com/thread/7946977

https://discussions.apple.com/thread/8027076