I'm not quite sure but I believe it's not possible to transfer accounts from ijji to aeria anymore because their database is lost or something. sorry..
you can try to write a ticket here: http://www.aeriagames.com/contact/support
but not sure if it can help you..
subcategory = other, game = a.v.a in English
write there your ijji username, your email you registered at ijji, your A.V.A character name.
but if you transferred your account some time ago then the problem might lie with Steam. log out from Steam before you go in game.