LDAP authentication issue

Hello,

I have 2 moodle instances running on the same server. One is 2.4.1 and the other is 2.5+. Both have the same LDAP setting, but I cannot login via LDAP on 2.5+. The error as below:

Unknown user, can not create new accounts:  myldapaccount

My enviroment: 

Server: Debian 7, php5-ldap, apache2.22, mysql 5.5.31, php 5.4.4-14

LDAP server: Windows AD

LDAP setting in moodle: ldap://ldapipaddress:3268

Please show me how to debug or fix it. Let me know if you need more information.

Thank you!