Pokemon Mystery Dungeon - Gates To Infinity Evolution with Stones?

[V!nce Unleashed]

I got a Sunstone (finally) and apparently, Petilil evolves with a sunstone.

So I gave my Petilil the sunstone, but once it levelled up, NOTHING happened. It didn't evolve.
So I used a Joy seed, but it still didn't evolve.

Yes, it was HOLDING the sunstone, and it says "Can Evolve!" in it's bio.
Why doesn't it evolve? Am I doing something wrong? It's a level 29...

 

[Altairis]

I searched online, and I think you have to go into a dungeon - you can't evolve outside of one. Try going in a dungeon and give Petilil the sunstone, and if that doesn't work level it up one more time with the sunstone while in a dungeon.