If your username is longer than I believe 16 letters, it won't allow you to login. Also symbols in a username can sometimes be glitchy. Also, check to make sure caps lock wasn't on.
If it is more than 16 letters, I'm sorry floof, but you'll have to make a new account in order to play. :c
Also, please don't make unnecessary polls. Just remember that for the future ^^
Hope this helps!