Let's say the following is in the HPEL or SystemOut log. Notice in this example that the authentication failure was caused by "login lockout".

[3/20/22 19:04:55:231 CDT] 00000ca0 LdapRegistryI E   SECJ0336E: Authentication failed for user cn=JohnDoe,ou=Users,ou=public,o=example because of the following exception javax.naming.OperationNotSupportedException: [LDAP: error code 53“ NDS error: login lockout (-197)]

And in this example, the authentication failure was caused by "connection refused". In this sceario, you may need to check for issues on the LDAP side.

[4/10/22 3:07:43:446 CDT] 00000001 LdapRegistryI E   SECJ0336E: Authentication failed for user cn=wasAdmins,ou=mgmt,ou=svcs,o=example because of the following exception javax.naming.CommunicationException: ldap.example.com:389 [Root exception is java.net.ConnectException: Connection refused (Connection refused)]

This shows that there are different things that can cause an authentication failure. This can occur when attempting to sign into the WebSphere admin console or when using command line tools that require authentication. 

In this example, the authentication failed when attempting to sign in as Bugs.

As the error implies, the most likely cause of this problem is the obvious one - the username or password provided in the request may be invalid.