Therealkendog wrote:
A used MacBook Pro was given to me as a gift, my user name and password was set. I tried to add a guest user and now there’s a lock asking for a password (mine does not work) I’m trying to go back and reset, turned off and on but nothing works please help.
https://discussions.apple.com/content/attachment/42b31f18-a97b-4970-a79a-8c90510f18ec
Doe not sound like this Mac was properly prepared ...What to do before you sell, give away, or trade in your Mac
Lock icon to protect against unauthorized access...

If your Mac is using a firmware password, the lock icon appears when you try to start up from another disk or volume, such as an external drive or macOS Recovery. Enter the firmware password to continue.
If you forgot your firmware password/do not have access to firmware password—
If you can't remember your firmware password, schedule an in-person service appointment with an Apple Store or Apple Authorized Service Provider ( Find Locations - Apple )
Bring your Mac to the appointment, and bring your original receipt or invoice as proof of purchase.