Solution
Make sure the user is in your users list in CUCM. Users can sign in even when the user is not imported into your Cisco WebEx Meetings Server database yet. When LDAP authentication is enabled and a user tries to sign in, your system checks if the email address exists in the database (local or remote user). If the user exists, it checks for the field
ADUserID in the database for this user. This field is populated after performing a directory synchronization. If this field is empty, then your system checks the CUCM database to see if this user exists there. If the user exists in the CUCM database, it updates the
ADUserID fields for this user record in the database and continues with authentication. Authentication succeeds as long as the user exists in the CUCM database and provides the correct credentials even though it was not previously synchronized using Directory Integration. After the first sign in, the user record is treated as an Active Directory synchronized user.