Why can't you evolve Buneary in Pokemon Mystery Dungeon Explorers of Time?

In mystery dungeon games, Pokemon don't just randomly evolve shen they are the right level, such as in trainer games. First you have to get your buneary to a high enough level, unlock the dungeon 'Luminous Spring' (Remembering to have only the buneary in your team) And evolve it there.

Hope this helped :D