I can access the GUI Admin page, but the Add and Delete is grayed out. I ran the permissions wizard and I have all the access rights necessary.
I also granted the User the Access with the Grant Unity Access Tool.
It sounds as though you need to run the DC/GC (Domain Controller/Global Catalog) Reconnect-tool (Commserver > Utilities or Tools Depot) as the server sounds like it's not connected. This will basically force reconnection. It isn't service affecting so you can run it anytime and monitor via the application logs to see when it finishes.
Is this affecting all subscribers or just one?
If this is just one person, have they been moved across mailstores recently or have any external Exchange/AD changes been made to their account?
If so you could try manually removing them from the SQL database and re-importing..
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