from the other side? what now?

Erm, is this a question of, "What do I need to get in?" or "I have it, but it won't open, it's a bug"?
There is an item you must acquire. Gend surely must have explained it all to you. Have you been to the Temple of Tyr yet? Or did you march right over to the tower? I realize that might be tempting and a character's first instinct, but there are missions here first.