Not able to find users from an active directory when adding to a collection

[RUSA]

Alteryx server 2021.1 x64

I have users from 2 different active directories, AB and YX. i.e., AB\janedoe and YX\johnsmith. When trying to add users to a collection I only see the users from the active directory AB. Is there a way to add users from YX?

I am also not able to create a group with YX users.

Thanks

[BrandonB]

You can find helpful information on Multi-Domain support here: https://help.alteryx.com/current/server/configure-gallery-authentication 

[RUSA]

I followed the directions for setup and I am the Default Gallery Administrator (domain\username). However, when adding users to a collection only users on a different domain are visible. Given a choice between the 2 domains, I would choose the one I am on because 90% of our users are in that domain. Is there a way to pick just one?

[BrandonB]

Do you have a service account configured that has permissions to read all attributes from both containers?