Why can’t I use my newly obtained characters in the Battle League/Legend League, the Guild Battle/Grand Battle, or the Tower of Souls?

If you see on the lower-left corner of the Party Formation screen of the Battle League/Legend League, the Guild Battle/Grand Battle, or the Tower of Souls, the new characters you obtained after the last time you locked the state of your characters’ gear will not be displayed.
This is because the states of your newly obtained characters’ gear are not locked, even when those characters have nothing equipped.

 

By opening the Lock Gear screen and tapping “Update,” the states of gear for all the characters in your roster will be updated and locked again. Doing this will lock the states of your newly obtained characters’ gear, allowing them to be displayed.

Also, by tapping “Unlock,” and making the Party Formation screen of the Battle League/Legend League, the Guild Battle/Grand Battle, or the Tower of Souls display , you can make it so that your newly obtained characters will always be displayed.