Password can't be "password"
Mediawiki refuses password
as password.
Also check that password match the rules raising the following error messages:
"passwordtooshort": "Passwords must be at least {{PLURAL:$1|1 character|$1 characters}}.",
"passwordtoolong": "Passwords cannot be longer than {{PLURAL:$1|1 character|$1 characters}}.",
"passwordtoopopular": "Commonly chosen passwords cannot be used. Please choose a password that is more difficult to guess.",
"password-name-match": "Your password must be different from your username.",
"password-login-forbidden": "The use of this username and password has been forbidden.",