NEAT is run by Orbitz not Asiana. It might be similar to an issue that I had before where my reservation was visible when I was logged in to MyAsiana but needed to log out to change seats. Depending on when your flight leaves you might be in the window where the seats are under airport control either for time or the fact that Asiana usually has a high percentage of seats blocked until check in. Even being Diamond Plus couldn't get a seat assignment. It might just the usual Asiana IT issue.