When attempting to log in with the vSphere Web Client, users have reported the error: Incorrect Username/Password The administrator has configured the Platform Services Controller Identity Source as:

A user entering the wrong password is the most direct cause of an incorrect username/password error, and should always be verified first before investigating infrastructure issues.

A one-way forest trust means that only one domain trusts the other - if the users' domain is in a forest with only a one-way trust toward vsphere.local's AD domain, their credentials cannot be validated through LDAP, causing authentication failure.

A two-way forest trust allows mutual authentication between forests, so users in a two-way trust environment would be able to authenticate successfully through the LDAP identity source.

Incorrect permissions in vCenter Server would result in an authorization error after login succeeds, not an 'Incorrect Username/Password' error during the authentication phase.