The cause is one of the followings. 

1

When registering, the user might have set the password to consist of only one identical number. (such as 1111)

For security measure, the password cannot be consisted of only one identical number.

Please register the password again. 

 

 2

The input password might be different to the registered password. 
When unable to recall the password, it is possible to register a new password to overwrite the old one.
※Old password is not necessary when registering a new password.