Quote Originally Posted by Enkidoh View Post
Welcome to Eorzea!

Lack of space in the Armoury Chest for rings can interefere with changing classes, but it can occur with any piece of gear, you might have to go through the entire Armoury Chest and ensure you have at least one empty slot in each to change, and then try changing your weapon again.
You may need two spaces free, I have a hard time switching if I only have one space free.