I'm trying to get the trophy for Catwoman that is where Mr Freeze and Nora are. I did the side mission for those two but it still won't let me into the building to get the trophy for the cat.
If I remember correctly you will need to get back into the building as Batman (I think you use a freeze grenade near the river in order to get in from underneath rather than the main door) and then you have to hack the door lock/security panel. Once you do this Catwoman will be able to get in and pick up the trophy.
I'm trying to find a guide/source for this, I will update when I do.
Edit: not the best source, but this question corroborates what I said.
By the way, it appears some players have experienced a bug where they would not be able to get into the room, even after unlocking it with Batman. For some, turning the game off and on again fixed the issue.