Hey
Welcome to the HP Support Forums!
I would like to assist you today with resetting the Administrator Password on your HP LaserJet Pro 200 color Printer M251n. At this time I am going to send you a Private Message with the instructions on how to perform an NVRAM Programming Reset on your printer.
Please refer to your Private Messages for further instruction.
If you feel that the Reset resolves this Administrator lock issue, please mark my post as a Solution so other users of the HP Support Forums can easily find these steps. Good luck! 