Code is Invalid?

[Shadowsun]

I tried entering in my pre-order code, but received a code is invalid message. After spending some time reviewing the pre-order FAQ, I realized that I purchased the game via Steam but purchased the pre-order via the Square Enix website. The two seem to be incompatible, which doesn't really make sense to me, but that's the way it is.

What should I do to resolve this situation?

Get a refund from Squenix Store, buy from Steam
And READ the product description and announcements.

Steam wants their cut of course so they are forcing people to buy the expansion from Steam if they already have purchased ARR from steam. Its business.
And they did warn people not to buy from other places and wait for the Steam pre-order if they were linked to steam already.