It is always a mess with SE registration codes.
There are in fact two mails for two codes.
pre-order access - you enter this one, you have access to the early access
full access - the key is given on a special web site, you should have a mail that tells you to download and activate the game. You have to consider this mail not as if you had already downloaded the game (that you actually did anyway for the early access) but as if you still had to do.
This is the confusing part that makes people to often consider they received two times the same message from the shop. It isn't the case, you have two mails for two access keys.
Try to find a mail you received between the realease date and lets says six days later. You should have a mail from the shop where you purchased the game.