My wife and I purchased two copies of this game and got into early access. We received a code that was something like "xxxxxx-###-xxxxxx-###" from Amazon called a "promotional code" with instructions to click on a link to unlock my early access to the game. Cool. Put this code in, got my access, happy camper. I also received a different code from Square-Enix, that was 5 groups of numbers/letters, such as "RAAU 354S R7TY XH56 Q34T" (obviously this is a random set of characters, not my code, but you get the point). The email from Square referred to this code as an "early access code" as well, but I unfortunately sort of glazed past this since I already had gotten an early access code from AMAZON, and assumed this was actually my key to create my account.
This is where things got all screwed up for me. Square-Enix has a place on their website that WILL ACCEPT this "early access" code as an account creation code and allow you to create an account. You get your mog hat, you get your Cait-Sith doll for the early access, and you login to the game expecting your CE items, which for me at least, never arrived. I followed several sets of instructions, trying to re-input my supposed CE code from Square-Enix, tearing my hair out, until FINALLY I found the solution to my problem and was able to collect my Collector's Edition items!
1) Go to your orders (on Amazon.com), and on the display of your FFXIV purchase there should be a button that says "Go to your games library."
2) Click "Go to your games library" and you will see your FFXIV. Next to and a little below the title, you will see a little yellow button that says "reveal code" or something to this effect. CLICK THIS.
3) Ta-da! A mysterious third code that looks nearly identical to the code provided by Square-Enix becomes available, and THIS CODE IS THE CODE YOU MUST APPLY TO YOUR ACCOUNT ON MOG STATION.
I hope this helps someone. Everyone was saying "You get two codes, you need to put them both in!" but in reality, I received not two but three codes, since for some reason I received two early access codes in two different formats, one from Amazon and one from Square-Enix. Maybe this has happened to you? Spread the word!