When administrator searches for a user that is in a different domain, despite the user being able to broker a session; in Director he gets this error message:

        User details cannot be retrieved from Active Directory. 
        Cannot find the user. View Director server event logs for further information.

In the event windows event viewer, nothing is logged.

Enable searches from an additional domain or forest by adding the name of the domain to the list. To do so:

    1. Log on to the server where director is installed
    2. Open Internet Information Services (IIS) Manager, You can use the inetmgr CMD command.
    3. Go to Host Name > sites > Default We Site > Director > Application Settings:

                 

    4. Change Connector.ActiveDirectory.Domains from "(user),(server)" to "(user),(server),<domain1>,<domain2>…":

               

    5. Repeat on all servers where Director is install

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Problem Cause

Director was not configured to search for the user in the additional domain.

By default, Director searches the global catalogue of the logged in admin’s domain and Director machine’s domain. You have to manually change web.config file for multi-domain environment 

When administrator searches for a user that is in a different domain, dispite the user being able to broker a session; in Director he gets this error message: User details cannot be retrieved from Active Directory.  Cannot find the user. View Director server event logs for further information. 

http://docs.citrix.com/en-us/xenapp-and-xendesktop/7-9/director/advanced-configuration.html#par_richtext_2
https://www.citrix.com/blogs/2016/09/12/using-citrix-director-in-a-multiforest-environment/