Well, firstly, did you check your account in the Mogstation to see if the items are actually listed there? If they're not, then you didn't register the preorder bonus code (although as you said you had early access to the expansion, so the items should be listed there). The only other thing I can think of is your Moogle Delivery Service inbox is full of 'reward' messages. The inbox can only hold a maximum 20 reward item messages, and so you will not receive any more if this limit is reached (you won't even get a notification).

Go to any moogle mailman and clear out your inbox (you can delete old reward messages as the items are no longer on them). Then log out and log back in and you should receive the item messages, however, if it still doesn't arrive, there is a button on the top corner of the Moogle mail inbox window along the lines of 'resend reward items' which if any item reward messages remain undelivered, they will be resent.