[ovirt-users] Unable to grant permissions to AD users

I'm having some issues granting permissions to AD users in ovirt-engine 4.1. Users can log in but receive an error as below. The user user@example.com(a)example.com is not authorized to perform login I am also not able to grant this user any permissions through the admin console. Entering a user name in the search field for the System Permissions section results in a blank list. Attached is a screenshot for reference. Does anybody have an idea on what would cause this? The log files aren't very useful and don't show any errors.