I am working on a SharePoint 2013 on-premise farm. We need to add a user "Subdomain\peterpan" to site collection A's permission group. But it returns "No exact match was found" error.
We checked in Central Admin -> Manage Profile Service: User Profile Service Application -> Manage User Profiles. The userID is found. Also we can add another user "Subdomain\alice" to that site collection A. In addition, we can add "Subdomain\peterpan" to another site collection B.
In the form assigning user permission, when I type in "Subdomain\" the dropdown list will show me "Subdomain\peterpan" (nothing else, only peterpan). When select it and click "Share" button, system return "user does not exist or is not unique" error.
In the user profile sync, we have setup to sync the DOMAIN.com. "Subdomain" is a child domain of DOMAIN.com.
What could cause the No exact match was found error?