On September 19th, ARRL changed the mechanism of password checking for Logbook of The World. The change took place at around 23:00 UTC on that date.
Prior to that date, the mechanism was not case-sensitive. But this was not a problem, as the system was generating passwords for the user. Users now can select their own passwords.
After the above change took place, the password checking mechanism has been made case-sensitive. This would cause a problem for users whose passwords contained upper-case characters, as the system would not recognise them.
If you are trying to login with your password which contains upper-case characters, try logging in with all lower-case characters. This should resolve the issue.