Like I said you need to read the Guide to get exactly what is needed here -'If you see the message "We're sorry, but this serial number is not valid. Please check your information and try again" and the Serial Number has passed verification at everymac.com then it is OK to use this Serial Number for your config.plist'. If you've checked your formulated S/N on everyman.com and it came back as a rig as close as possible a Mac model to your setup, then despite what it says on the Apple site, as long as it says 'invalid' you are good to go. I don't know how much clearer I can make the process for you to understand. Good luck.