Whatever is flagging your username as incorrect because of capitalization is wrong, not that you can fix someone else's code. AOL never complained if I used dmcritchie or DMcRitchie but I lost out on something else because someone else thought my AOL email address did not match their own database requirements. Email addresses are not case sensitive.

Delete the entry choice offered for userid dropdown that you get by double-click within the userid field, by using "Shift+Del" on your Mac, simply "Del" on other systems. Then reenter your userid in lowercase. If that doesn't work you may have to delete a cookie in privacy, and/or a user/password in security.

Make sure that you haven't saved multiple (uppercase, lowercase) versions of that name and password.

Remove saved Password(s):

• Firefox > Preferences > Security: Passwords: "Saved Passwords" > "Show Passwords"