Connection to LDAP Server Failed;Check User Credentials

Hi

On a EP7 SP18 System, I am trying to test connection to LDAP server.

After entering the Required information i get the error:

Connection to LDAP Server Failed;Check User Credentials

User credentails are correct and we can login to the domain using the same credentails

from windows.

we had done a similar test previously and that time it worked perfectly.

we also did a ping test from portal server to LDAP server andit is also working fine.

what can be the problem ?

Regards

Rajendra