Following might be the possible reasons:

1．The passwords you enter do not meet the length requirements.
The length of passwords must be within 6-20 characters; otherwise they cannot be accepted by the system.

2．The passwords you enter contain illegal characters.
The passwords should only be composed of English alphabets and Arabic numerals. The system does not accept punctuations, blank, *, @, and other characters.

3．your password coincides with your username.
For the sake of Internet information security, the system requires that the password must differ from your username.