MAC addresses are becoming a bit useless for copy-protection nowadays… In the old days a machine might have a couple of addresses that stayed constant, but these days you get things like VM software that generates lots of temporary fake addresses on the fly, making them much less reliable than they used to be.
I did change the way they were detected a few months ago, because the old methods I was using had become a bit out-of-date. The newer code will probably find more addresses than the old code did, but should still find all the old addresses that it used to.
Whenever I’ve used MAC addresses in my own copy-protection, I tend to keep a list of all the addresses, and then when checking, I’d consider it a positive match if at least 1 or 2 of them remain constant. Not very reliable, but there’s no way to tell the ‘fake’ ones from the real ones any more.