Enabling Active Directory Authentications in service desk

Enabling Active Directory Authentications in service desk

hello ! i am new to this forum. I installed ManageEngine 8.1 in test environment. I am able to import requesters from Active directory but when i enable self-service web portal to requesters and try to login with requester AD user and password, it not logging and returns the message username or password not correct and login screen pops again. 
What i am missing in the configuration ?

thank you 

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