MY MAC BOOK PRO is locked after having been placed in Lost Mode via Find My Iphone. I cannot get it to accept the code that I input when I placed it into lock mode. It continues to stay in a perpetual state of disability (for 60 minutes at a time).

MY MAC BOOK PRO is locked after having been placed in Lost Mode via Find My Iphone app. I cannot get it to accept the code that I input when I placed it into lost mode. It continues to stay in a perpetual state of disability (for 60 minutes at a time). Have tried to erase it but I cannot get into a position where I can do anything. All I can do is shut it down and then if I press the option, command, P, & R keys simultaneously, when I turn it on, I can input the code which never works.