Unfortunately the old address that doesn't work any more is the one I used to sign up to the beta, many months ago.
Understandably, signing up multiple times in the hopes of getting selected isn't allowed and there are probably measures to prevent such abuse (IP recognition, name & other personal details recognition, etc.)
What can I do? If I've been selected very recently I won't receive that email, and I can't find a way to change it other than registering again...