Fantasia isn't like a name change -- you right click your character on the list of your characters screen and press 're-edit appearance' or something like that. If you left click as normal, you simply log in.
It is worth noting that due to the servers being rammed with players, I, too have been unable to use my Fantasia. But this is not a bug, it's normal to preserve server load. You can tell when this is happening when it shows lots of ???'s regarding your character's location and so on.