I tried that, but when I tried signing in with my new one, it said "Incorrect Username." Then I proceeded to use my older one and it let me log in. Where it says "Hello, *Username* It says my new username though, but I want to be able to sign in with that same name.
Edit: Just tried again a few hours later and the same results occured. I cannot sign-in with my new username. Is there any solution to this issue?