After inputting your username and password to page, you are encountering an error message that says, "Try again after some time or contact your help desk"

"Rejecting with error code 4009“，”receive_ldap_user_search_event:ldap_first_entry_returned null, user XXX not found“ could be found via NetScaler aaad.debug module .
In brief, the error message "Rejecting with error code 4009" indicates that a user with the identifier "XXX" was not found during an LDAP user search, leading to the rejection of the authentication attempt.

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Set  "Server Logon Name Attribute"  in LDAP Sever "LDAP_OTP_set_no_auth" to "sAMAccountName"
 

Problem Cause

"Server Logon Name Attribute"  in LDAP Sever "LDAP_OTP_set_no_auth" was incorrectly set to "sAMAccount" instead of "sAMAccountName"

NetScaler Gateway OTP authentication fails with error 4009 because the LDAP Server Logon Name Attribute is incorrectly configured as sAMAccount instead of sAMAccountName.

NetScaler Gateway OTP Setup Guide from Carlstalhood