Same Issue but Horrible Result
	
	
		I got the second registration code for mine and used it to regsiter the game during the Early Access. Now when I try to log in, it's asking for the code again and saying that it's invalid/already used when I try to reenter the code.
Sounds like their system didn't register the codes properly during early access and if you used it, you're locked out now. And SE support isn't open until Monday so looks like everyone is stuck waiting til then.
On a side note, the PS4 versions has no issue registering because it was done automatically.