Users do not show up in the work queue as an assigned worker

I am not sure where to start with this problem.

I have users in one of my domains. NONE of them show up as an assigned worker in the queues in helpdesk. The Microsoft® Active Directory Import works and I can see them in the console user list. I see them as a worker when I list workers. Even emails are sent to them when an incident is put in there work queue.

All four of my other Domains work..

Everything looks the same and should be working..

The differences are that this domain only has one plant in it and the users are located in a different container.

ANY help would be great....