Possible Bug - Ivy Level Lock not triggering?

So fairly new to this game, and really enjoying it so far. But hit what I think is a bug which is kind of bumming me out.

So I've just completed the first part of the story, getting the three main characters to 25, and Ivy to 10. But now Ivy is still locked at 10, with the only requisite for releasing the level lock being getting the three characters to 25, which I already have.

I've tried leveling them up further, but nothing seems to trigger the lock to be undone. Is this a bug, or am I missing something here?

I'm on Android as well, if that matters.