I was able to go to my orders in the SE store, where I bought the expansion, and unlock the code.

I am very baffled by the way SE handles these codes. First, when I got my pre order early access code, I got ONE code, that I had to go to a site and enter to get a SECOND code to get early access, and now there's a THIRD code I need despite it already verifying early access meaning it already verified a purchase of the expansion? This seems just overly convoluted.

I hope they streamline this for 6.0.