I tried to update my MacPro (mid 2010) running High Sierra (10.13.6). I kept finding that it wouldn't update because I couldn't update the firmware.
I disabled BitDefender, and eventually completely removed it but that didn't help. There was nothing else that could have interfered with the updates.
I contacted Apple support and over three days the tech support guy couldn't figure out what the problem was. He thought the problem was a slow or interrupted internet connection.
I contacted BitDefender support and they sent me something that would capture what was gong on with the MacPro that was refusing to allow the update (take screen shots of the terminal or something like that). While trying to follow the directions I had to go into Terminal and type in commands. At that point I got a message that the firmware was locked and I couldn't proceed until I unlocked it.
So the good news is that I now know why I can't update the firmware, but I have no idea how to unlock it.
It took me awhile to remember buying some anti virus software back when I first bought the computer and it had a screen that asked to lock the firmware so that my Mac couldn't be accessed remotely. I checked "yes" and totally forgot about it. Now it has come back to haunt me.
I tried all the old passwords that I had on file but nothing worked. I never use the Terminal or any of the advanced features so I am at a total loss here. Anyone with any ideas? I am several hours away from an Apple genius/store. But that may be my only option. Any better (and more convenient) ideas would be great.