Check to make sure your serial number is valid.

Using a newer Mac, go to https://checkcoverage.apple.com

Enter the Mac's serial number (the one you are fixing, not the one with the webpage), and a code that Apple makes you put in.

If the Mac's year shows up, then you can fix the issue in About this Mac.

If the year does NOT show up, then your serial number is invalid, or your machine was specially built, and therefore About this Mac will not work anyway.